Lens barrel, lens driving apparatus, camera, and mobile information terminal

ABSTRACT

A lens barrel includes a plurality of lens groups each having at least one lens; a plurality of lens retaining frames which retain a corresponding one of the plurality of lens groups; a telescopic cylinder containing therein the plurality of lens groups and the plurality of lens retaining frames; a lens retaining frame driving device configured to drive at least one of the lens retaining frames; a moving member which moves in a direction along the photographing optical axis; and a position detector configured to detect a change in a position of the moving member, wherein the plurality of lens retaining frames including a retractable lens retaining frame configured to retract the at least another one of the plurality of lens groups from the photographing optical axis to a retracted position out of the telescopic cylinder in the collapsed state.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 11/908,018, filed Sep. 7, 2007, now U.S. Pat. No. 7,595,940,which is a 371 of PCT/JP2006/304818, filed Mar. 6, 2006, and based onand claims priority benefit from Japanese Patent Application No.2005-063318, filed Mar. 8, 2005, the entire contents of each of whichare hereby incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention generally relates to a lens barrel in which eachlens group is collapsed in one form and each of the lens groups isextended out to a predetermined position to be used in another form.More particularly, the invention relates to a lens barrel suitable for azoom lens capable of changing a focal distance by relatively moving aplurality of lens groups, a lens driving apparatus, a camera, and amobile information terminal using the lens barrel.

BACKGROUND ART

Conventionally, in an imaging device such as a digital camera, withadvance in a high performance of a lens barrel having a zoom lensfunction capable of changing a focal distance, or miniaturization of theimaging device according to the user's demand, there has beenincreasingly used a lens barrel in which a plurality of lens groups iscollapsed when photographing is not carried out. Furthermore, because ofthe demand for not only simple reduction in dimension, but also furtherreduction in thickness, it is now important to reduce the thickness ofthe lens barrel in a collapsed position to the maximum extent.

As a technology to cope with the demand for reduction in thickness ofthe lens barrel, there has been used a lens barrel in which a lenscylinder retaining therein a plurality of lens groups is collapsed intothe imaging device when not in use, and one of the lens groups isretracted out of an optical axis of the lens groups when the lens groupsare collapsed.

A technology for retracting one of lens groups out of an optical axis isdisclosed in, for example, JP 2003-315861A (Patent Document 1) and JP2003-149723A (Patent Document 2). According to the structure disclosedin each of the Patent Documents 1 and 2, a mechanism is employed whereinan optical axis of a lens group retained by a retractable lens retainingframe is estranged from an optical axis of other lens group when thelens groups are collapsed and the optical axis of the lens group of theretractable lens retaining frame is made to coincide with the opticalaxis of other lens group when the photographing is being carried out.Since one of a plurality of lens groups disposed on the optical axis isretracted out of the optical axis when the lens groups are collapsed,the entire dimension of the lens barrel in a direction of the opticalaxis can be reduced, so that the thickness of the imaging device isreduced.

Note that, in the structure disclosed in Patent Documents 1 and 2, thelens retracted out of the optical axis is actually positioned within alens cylinder provided in the lens barrel to retain therein the lensgroups, even after the lens is retracted.

However, according to a structure of a conventional technology such asthose disclosed in the Patent Documents 1 and 2, there has been aproblem that it is difficult to accurately grasp a change in positionsof the retractable lens retaining frame when the optical axis of thelens group retained by the retractable lens retaining frame is made tocoincide with or estranged from the optical axis of other lens group ina transition from a collapsed state to a photographing state or from thephotographing state to the collapsed state. There has been also aproblem that it is difficult to accurately grasp displacement of theretractable lens retaining frame in an optical axis direction coaxialwith the optical axis of other lens group when the photographing isbeing carried out. Further disadvantage of the conventional technologyis that a mechanism for detecting the position of the retractable lensretaining frame in a direction estranging from the optical axis of otherlens group and/or a mechanism for detecting the position of theretractable lens retaining frame in the optical axis direction coaxialwith the optical axis of other lens group, become complicated.

DISCLOSURE OF THE INVENTION

The present invention has been made in view of the above-mentionedcircumstances, and therefore, at least one objective of the presentinvention is to provide a lens barrel capable of detecting a position ofa retractable lens retaining frame with high accuracy, a lens drivingapparatus, a camera, and a mobile information terminal using the lensbarrel.

To achieve these and other advantages and in accordance with the purposeof the invention, as embodied and broadly described herein, theinvention provides a lens barrel, comprising: a) a plurality of lensgroups each having at least one lens; b) a plurality of lens retainingframes each retaining corresponding one of the plurality of lens groups;c) a telescopic cylinder containing therein the plurality of lens groupsand the plurality of lens retaining frames; d) a lens retaining framedriving device configured to drive at least one of the lens retainingframes; at least one portion of the plurality of lens groups beingcollapsed to store the plurality of lens groups in a collapsed state andat least one portion of the plurality of lens groups being moved towarda subject in a photographable state, the plurality of lens retainingframes including a retractable lens retaining frame configured to retainand retract at least one of the plurality of lens groups to a retractedposition substantially out of the telescopic cylinder in the collapsedstate and configured to move the corresponding at least one of theplurality of lens groups from the retracted position to a photographingposition in the photographable state such that an optical axis of thecorresponding at least one of the plurality of lens groups substantiallycoincide with an optical axis of the other lens group of the pluralityof lens groups in order that all of the plurality of lens groups besubstantially aligned on the same optical axis; and e) a positiondetector configured to detect a change in a position of the retractablelens retaining frame in the collapsed state and in the photographablestate, the retractable lens retaining frame including a cam portionconfigured to change a position of the retractable lens retaining framebetween the retracted position which is substantially out of thetelescopic cylinder and which is distant from the optical axis of saidthe other lens group, and the photographing position in which theoptical axis of the corresponding at least one of the plurality of lensgroups retained by the retractable lens retaining frame is positionedsubstantially on the optical axis of said the other lens group and inwhich the retractable lens retaining frame is moveable in a directionsubstantially coaxial with the optical axis of said the other lensgroup, so as to detect, based on an amount of a displacement of theretractable lens retaining frame in the direction substantially coaxialwith the optical axis of said the other lens group, a displacement ofthe retractable lens retaining frame in a direction in which the opticalaxis of the corresponding at least one of the plurality of lens groupsretained by the retractable lens retaining frame approaches andseparates away from the optical axis of said the other lens groupbetween the collapsed state and the photographable state, and adisplacement of the retractable lens retaining frame in the directionsubstantially coaxial with the optical axis of said the other lens groupin the photographable state, the lens retaining frame driving deviceincluding a lead screw configured to advance and retreat the retractablelens retaining frame in a direction substantially extending parallelwith the optical axis of said the other lens group, and a female screwmember screwed on the lead screw and capable of being advanced andretracted by rotation of the lead screw in an axial direction of thelead screw which extends substantially in parallel with the optical axisof said the other lens group, the female screw member including acontact portion configured to contact with the cam portion to change theposition of the retractable lens retaining frame between the retractedposition and the photographing position by the rotation of the leadscrew, and the position detector including a detected portion providedon the female screw member so as to detect the position of the femalescrew member in the axial direction at the time of the rotation of thelead screw, and a detecting portion arranged in an area of movement ofthe detected portion for detecting a displacement of the detectedportion in the axial direction.

Following are preferred embodiments (1) to (6) of the lens barrelaccording to the present invention. Any combinations thereof may beconsidered to be preferred ones of the present invention unless anycontradictions occur.

-   (1) The position detector is configured to generate a reference    signal indicating that the retractable lens retaining frame is    located at the retracted position so as to change a state of the    retractable lens retaining frame from the collapsed state to the    photographable state, before moving the retractable lens retaining    frame from the retracted position to the photographing position so    as to substantially coincide the optical axis of the corresponding    at least one of the plurality of lens groups retained by the    retractable lens retaining frame with the optical axis of said the    other lens group.-   (2) The position detector is configured to generate an entering    completed signal indicating that entering of the optical axis of the    corresponding at least one of the plurality of lens groups retained    by the retractable lens retaining frame on the optical axis of said    the other lens group from the retracted position to the    photographing position has completed, after the state of the    retractable lens retaining frame has changed from the collapsed    state to the photographable state.-   (3) The position detector is configured to output a positional    reference signal in an optical axis direction so as to displace the    retractable lens retaining frame in the direction substantially    coaxial with the optical axis of said the other lens group for    performing photographing, after the optical axis of the    corresponding at least one of the plurality of lens groups retained    by the retractable lens retaining frame has approached on the    optical axis of said the other lens group from the retracted    position to the photographing position.-   (4) At least one optical element located nearer to an image plane in    the lens barrel than the retractable lens retaining frame is    included, and wherein the position detector permits movement of the    optical element after generating the entering completed signal of    the retractable lens retaining frame at the time when the state of    the retractable lens retaining frame has transited from the    collapsed state to the photographable state.-   (5) The detected portion is substantially in an alphabet T    configuration.-   (6) The detected portion is substantially in an alphabet L    configuration.

The present invention also provides a lens driving apparatus, comprisingthe lens barrel according to any one of the lens barrel mentioned above.

The present invention further provides a camera, comprising the lensbarrel according to any one of the lens barrel mentioned above.

The present invention further provides a mobile information terminal,comprising the lens barrel according to any one of the lens barrelmentioned above.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the invention as claimed.

EFFECT OF THE INVENTION

In the lens barrel according to the present invention, at least oneportion of the plurality of lens groups, each having at least one lens,is collapsed to store the plurality of lens groups in the collapsedstate and at least one portion of the plurality of lens groups is movedtoward the subject in the photographable state.

In order to attain the movement between the collapsed state and thephotographable state as well as to attain miniaturization, the lensbarrel according to the present invention is provided with the pluralityof lens retaining frames each retaining corresponding one of theplurality of lens groups, the telescopic cylinder containing therein theplurality of lens groups and the plurality of lens retaining frames, andthe lens retaining frame driving device configured to drive at least oneof the lens retaining frames.

The plurality of lens retaining frames includes the retractable lensretaining frame configured to retain and move at least one of theplurality of lens groups, so that the lens barrel according to thepresent invention is possible to retract at least one of the pluralityof lens group to the position more out than the telescopic cylinder oroutside of the maximum outer diameter of the telescopic cylinder in thecollapsed state and to position the corresponding at least one of theplurality of lens groups retained by the retractable lens retainingframe such that all of the plurality of lens groups are substantiallyaligned on the same optical axis.

The lens barrel including the retractable lens retaining frame isdetectable of the displacement of the retractable lens retaining framein the direction in which the optical axis of the corresponding at leastone of the plurality of lens groups retained by the retractable lensretaining frame approaches and separated away from the optical axis ofother lens group between the collapsed state and the photographablestate, and the displacement of the retractable lens retaining framechanging in the direction substantially coaxial with the optical axis ofother lens group in the photographable state, by the displacement amountof the retractable lens retaining frame in the direction substantiallycoaxial with the optical axis of other lens group.

In addition, in order to switch over from the collapsed state to thephotographing state and from the photographing state to the collapsedstate, the retractable lens retaining frame is formed with the camportion for changing the position of the retractable lens retainingframe between the retracted position which is substantially out of thetelescopic cylinder and which is distant from the optical axis of otherlens group, and the photographing position in which the optical axis ofthe corresponding at least one of the plurality of lens groups retainedby the retractable lens retaining frame is positioned substantially onthe optical axis of other lens group and in which the retractable lensretaining frame is moveable in the direction substantially coaxial withthe optical axis of other lens group.

Moreover, the lens retaining frame driving device is provided with thelead screw configured to advance and retreat the retractable lensretaining frame substantially in parallel with the optical axis, and thefemale screw member screwed on the lead screw to be capable of beingadvanced and retracted by the rotation of the lead screw in the axialdirection of the lead screw.

The female screw member is provided with the contact portion whichcontacts with the cam portion to change the position of the retractablelens retaining frame between the retracted position and thephotographing position by the rotation of the lead screw.

In addition, the position detector, which detects the change in theposition of the retractable lens retaining frame in the collapsed stateand in the photographable state, includes the detected portion providedon the female screw member for detecting the position of the femalescrew member in the axial direction, which is substantially in parallelwith the optical axis, when the lead screw rotates. The positiondetector also includes the detecting portion arranged in the moving areaof the detected portion in order for detecting the displacement of thedetected portion in the axial direction.

Therefore, when the lead screw is rotated and thus the female screwmember moves in the axial direction of the lead screw, the contactportion of the female screw member contacts with the cam portion, andthereby, it is possible to change the position of the retractable lensretaining frame having the cam portion from the retracted position tothe photographing position, to move the retractable lens retaining frameforward and backward in the optical axis direction in the photographingposition, and to return the retractable lens retaining frame from thephotographing position to the retracted position.

In addition, the detected portion of the female screw member isconfigured to be detected by the detecting portion. Hence, it ispossible to accurately detect that the retractable lens retaining frameis at the retracted position, the retractable lens retaining frame is inthe state of changing from the retracted position to the photographingposition, the photographing position of the retractable lens retainingframe in the photographable state, the retractable lens retaining frameis in the changing state from the photographing position to theretracted position, and so on, based on the position at which thedetected portion is located.

Therefore, it is possible to detect changes in a state in the lensbarrel promptly and accurately, and hence, operation from activation ofa device installed with the lens barrel according to the presentinvention to completion of photographing can be promptly carried out toimprove ease of use.

Here, coinciding of the optical axis of the lens group retained by thelens retaining frame with the optical axis of other lens group withinthe plurality of lens group and separating of the optical axis of thelens group retained by the retaining frame from the optical axis ofother lens group may be attained by a structure which swings around acenter point provided with the retractable lens retaining frame.Alternatively, a mechanism which allows the retractable lens retainingframe to enter into and evacuate from the optical axis of other lensgroup in a direction perpendicular to the optical axis of other lensgroup may be employed.

Also, according to one aspect of the lens barrel according to thepresent invention, the reference signal indicating that the retractablelens retaining frame is located at the retracted position is generatedby the position detector so as to change the state of the retractablelens retaining frame from the collapsed state to the photographablestate, before moving the retractable lens retaining frame from theretracted position to the photographing position for substantiallycoinciding the optical axis of the corresponding at least one of theplurality of lens groups retained by the retractable lens retainingframe with the optical axis of other lens group. Therefore, it ispossible to determine reference time for the retractable lens retainingframe to change from the retracted position to the photographingposition. Since the number of rotation of the lead screw and a feedingpitch of the female screw member are previously known, it is possible toaccurately grasp the position of the retractable lens retaining framefrom the number of rotation of the feed screw and an amount of feedingof the pitch of the female screw member after elapse of the referencetime.

According to one aspect of the lens barrel according to the presentinvention, the position detector generates the entering completed signalindicating that entering of the optical axis of the corresponding atleast one of the plurality of lens groups retained by the retractablelens retaining frame on the optical axis of other lens group from theretracted position to the photographing position has completed, afterthe state of the retractable lens retaining frame has changed from thecollapsed state to the photographable state. Therefore, it is possibleto accurately grasp the position of the retractable lens retaining framein the optical axis direction at the time of the generation of theentering completed signal, so that it is possible to obtain a focusingposition in the photographing, accurately.

According to one aspect of the lens barrel according to the presentinvention, the position detector outputs the positional reference signalin the optical axis direction so as to displace the retractable lensretaining frame in the direction substantially coaxial with the opticalaxis of other lens group for performing photographing, after the opticalaxis of the corresponding at least one of the plurality of lens groupsretained by the retractable lens retaining frame has approached on theoptical axis of other lens group from the retracted position to thephotographing position. Therefore, it is possible to accurately detectthe position of the retractable lens retaining frame in the optical axisdirection.

According to one aspect of the lens barrel according to the presentinvention, at least one optical element (for example, a lens) locatednearer to the image plane in the lens barrel than the retractable lensretaining frame is further provided, and the position detector permitsthe movement of the optical element after generating the enteringcompleted signal of the retractable lens retaining frame at the timewhen the state of the retractable lens retaining frame has transitedfrom the collapsed state to the photographable state. Therefore, it ispossible to prevent an interference of the optical element with theretractable lens retaining frame, and also to shorten the time requiredfrom turning ON of the device having the lens barrel according to thepresent invention to a point of time in which lenses are protruded to bephotographable, so that ease of use is attained.

Also, according to the present invention, the lens barrel comprises theplurality of lens retaining frames which include the retractable lensretaining frame configured to retain and retract at least one of theplurality of lens groups to the retracted position more out than thetelescopic cylinder in the collapsed state and to move and position thecorresponding at least one of the plurality of lens groups from theretracted position to the photographing position in the photographablestate such that the optical axis of the corresponding at least one ofthe plurality of lens groups substantially coincides with the opticalaxis of other lens group of the plurality of lens groups in order thatall of the plurality of lens groups are substantially aligned on thesame optical axis. Therefore, it is possible to effectively minimize asize in the optical axis direction of the device installed with the lensbarrel according to the present invention without extremely increasing adimension within a plane transverse to the optical axis.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this description. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a perspective view showing a structure of a main part of anoptical system device including a lens barrel according to a firstembodiment of the present invention with lens groups collapsed, asviewed from a subject.

FIG. 2 is a perspective view showing the main part of the lens barrelshown in FIG. 1, as viewed from an imaging plane.

FIG. 3 is a schematic perspective view showing a structure of a mainpart of the optical system device including the lens barrel in which alens barrier is closed with the lens groups collapsed, as viewed fromthe subject.

FIG. 4 is a schematic perspective view showing the structure of the mainpart of the lens barrel shown in FIG. 3, as viewed from the imagingplane.

FIG. 5 is a schematic perspective view of the structure of the main partof the lens barrel in a state in which the lens barrier is opened in aphotographing state with the lens groups extended, as viewed from theimaging plane.

FIG. 6 is a perspective view of the structure of the main part of thelens barrel in the photographing state with the lens groups extended, asviewed from the imaging plane.

FIG. 7 is a perspective view of a layout of a third frame, an impactpreventing member, and a fourth frame in a state in which the lensgroups are in a collapsed position, for explaining operations of thethird frame which retains the third lens group and the impact preventingmember, as viewed from the subject.

FIG. 8 is a perspective view of a layout of the third frame, the impactpreventing member, and the fourth frame for explaining operations of thethird frame, which retains the third lens group, and theimpact-preventing member in the photographing state with the lens groupsprojected, as viewed from the subject.

FIG. 9A and 9B is a vertical cross sectional view showing, in an upperhalf and a lower half with respect to an optical axis, main parts of thelens groups, the lens retaining frames, and the various lens cylindersof the lens barrel in the photographing state in which the lens groupsare extended, and in a collapsed state in which the lens groups areretired to be collapsed, respectively.

FIG. 10 is a schematic development elevational view showing a shape ofcam grooves formed on a second rotary cylinder in a developed state.

FIG. 11 is a schematic development elevational view showing a shape ofcam grooves formed on a cam cylinder in a developed state.

FIG. 12 is a schematic development elevational view showing a shape ofcam grooves and key grooves formed on a first liner in a developed statewith a helicoid omitted.

FIG. 13A is a schematic development elevational view showing a shape ofcam grooves and key grooves formed on a fixed frame in a developed statewith the helicoid omitted, FIG. 13B is a schematic developmentelevational view showing the shape of the cam grooves and the keygrooves formed on the fixed frame in the developed state with thehelicoid, and FIG. 13C is a perspective view showing an externalappearance of a first rotary cylinder fitted to the helicoid.

FIG. 14A is a side view showing a structure of the third frame and itsdrive system, and FIG. 14B is a perspective view of FIG. 14A.

FIG. 15A is a schematic perspective view showing the structure of thethird frame and its drive system, and FIG. 15B is a view schematicallyshowing an assembled state of the third frame and its drive system.

FIG. 16A is a front view of the third frame part for explainingoperation of the third frame, as viewed from the imaging plane, and FIG.16B is a perspective view mainly showing a shutter part.

FIGS. 17A and 17B are schematic perspective views showing an exteriorappearance and a structure of a camera according to a second embodimentof the present invention as viewed from the subject, wherein FIG. 17Ashows a state in which a photographing lens is collapsed in a body ofthe camera, and FIG. 17B shows a state in which the photographing lensis projected or extended from the camera body.

FIG. 18 is a perspective view schematically showing the exteriorappearance and structure of the camera of FIGS. 17A and 17B as viewedfrom a user.

FIG. 19 is a block diagram schematically showing a functional structureof the camera of FIGS. 17A and 17B.

FIG. 20A is a perspective view schematically showing a fourth frame anda main part of its drive system, and FIG. 20B is a perspective viewshowing the fourth frame and the main part of its drive system in whicha part of those is omitted and seen from a different angle.

FIG. 21 is a block diagram schematically showing a structure of a drivecontrol system.

FIG. 22 is a timing chart showing a sequence when the lens barrier isoperated from a closed position to an opened position in an activationsequence.

FIG. 23 is a timing chart showing a sequence in which the lens barrieris operated from the opened position to the closed position in theactivation sequence.

FIG. 24A is a table showing a reset sequence of the lens barrel, andFIG. 24B is a timing chart of HP signals.

FIG. 25 is a timing chart showing a storage sequence in a state in whichthe lens barrier is operated to close.

FIG. 26 is a flow chart showing a zoom sequence.

FIG. 27 is a timing chart showing a zoom sequence of zooming from thewide angle to the telephoto.

FIG. 28 is a timing chart showing a zoom sequence of zooming from thetelephoto to the wide angle.

FIG. 29 is a perspective view showing a posture of the third frame in aretracted state.

FIG. 30 is a perspective view showing the posture of the third frame inthe retracted state seen from a different angle.

FIG. 31 is a perspective view showing a mounted state of the fixed frameand the third frame.

FIG. 32 is a view showing a combined state of the third frame and acompression torsion spring.

FIG. 33A is a view showing a contacted state of a cam portion and anabutting portion of a third frame female screw member when the thirdframe is in the retracted state, and FIG. 33B is a view showing acontacted state of the cam portion and the abutting portion of the thirdframe female screw member when the third frame changes from theretracted state to the photographing state.

FIG. 34 is a view showing a positional relation of a T-shaped protrudedmember of the third frame female screw member and a photo-interrupterwhen the T-shaped protruded member passes between a light-emittingdevice and a light-receiving device of the photo-interrupter.

FIG. 35 is a view showing a positional relation of an L-shaped protrudedmember of the third frame female screw member and the photo-interrupterwhen the L-shaped protruded member passes between the light-emittingdevice and the light-receiving device of the photo-interrupter.

FIG. 36 is a timing chart representing a sequence when the lens barreltransits from the collapsed state to a telephoto state.

DESCRIPTION OF NUMERALS

-   11 First lens group-   12 Second lens group-   13 Third lens group-   14 Fourth lens group-   15 Shutter/aperture stop unit-   16 Solid-state image-sensing device-   17 First frame-   18 Cover glass-   19 Low-pass filter-   21 Fixed frame-   22 First rotary cylinder-   23 First liner-   24 Second rotary cylinder-   25 Second liner-   26 Cam cylinder-   27 Lineally-moving cylinder-   31 Third frame-   32 Third group main-guide shaft-   33 Third frame sub-guide shaft-   34 Third group lead screw-   35 Third frame female screw member-   36 Impact-preventing member-   37 Compression torsion spring-   38 Third-frame photo-interrupter-   41 Fourth frame-   42 Fourth frame sub-guide shaft-   43 Fourth frame spring-   44 Fourth frame main-guide shaft-   45 Fourth frame lead screw-   46 Fourth frame female screw member-   47 Fourth group photo-interrupter-   51 Zooming motor-   52 Third frame drive motor-   53 Fourth frame drive motor-   61 Barrier control member-   62 Lens barrier-   63 Barrier drive system-   71 Gear-   72 Gear-   73 Gear-   74 Gear-   81 Retainer plate-   82 Lens barrel base-   101 Image pickup lens-   102 Shutter release button-   103 Zoom lever-   104 Viewfinder-   105 Strobe light-   106 Liquid crystal display (LCD)-   107 Operating button-   108 Power switch-   109 Memory card slot-   110 Expansion card slot-   201 Photodetector-   202 Signal-processing unit-   203 Image-processing unit-   204 Central processing unit (CPU)-   205 Semiconductor memory-   206 Expansion card-   301 Barrier-operating element-   350 T-shaped protruded member (position detector)-   351 Photo-interrupter (position detector)-   501 Central calculation processing device-   502 Motor driver-   503 First and second frames DC motor-   504 First aperture stop motor-   505 Second aperture stop motor-   506 Shutter motor-   507 Third frame pulse motor-   508 Fourth frame pulse motor-   509 First and second frames photo-interrupter-   510 First and second frames photo-reflector-   512 Fourth frame photo-interrupter-   513 First and second frames photo-interrupter drive circuit-   514 First and second frames photo-reflector drive circuit-   515 Third frame photo-interrupter drive circuit-   516 Fourth frame photo-interrupter drive circuit

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the present preferredembodiments of the present invention, examples of which are illustratedin the accompanying drawings. Wherever possible, the same referencenumbers are used in the drawings and the description to refer to thesame or like parts. The scope of the present invention, however, is notlimited to these embodiments. Within the scope of the present invention,any structure and material described below can be appropriatelymodified.

FIGS. 1 to 16B and 20 illustrate a first embodiment of a lens barrelaccording to the present invention.

In FIGS. 1 to 16B and 20, the lens barrel includes a fixed frame 21having a fixed cylinder 21 a, a telescopic cylinder unit or telescopiccylinder attached to the fixed frame 21, and a plurality of lens groupsdisposed in the telescopic cylinder. The telescopic cylinder is movableand collapsible along an optical axis X of the plurality of lens groups.

The lens groups comprise, for example, a first lens group 11, a secondlens group 12, a third lens group 13, and a fourth lens group 14, whichare disposed in the telescopic cylinder (see FIG. 9).

The telescopic cylinder includes, for example, a first rotary cylinder22, a first liner 23, a second rotary cylinder 24, a second liner 25, acam cylinder 26, a lineally-moving cylinder 27, and a third frame 31(see FIGS. 5 and 8) for retaining the third lens group 13. As describedbelow, the first rotary cylinder 22 and so on are moved along theoptical axis with respect to each other with the plurality of lensgroups 11 to 14.

As shown in FIG. 9, the first, second, third, and fourth lens groups 11,12, 13, and 14 are positioned from a subject (not shown) in sequence anddisposed on the optical axis X. A shutter/aperture stop unit 15 isdisposed between the second lens group 12 and the third lens group 13.The first, second, third, and fourth lens groups 11, 12, 13, and 14, andthe shutter/aperture stop unit 15 are configured to be movable in adirection of the optical axis when the telescopic cylinder is movedalong the optical direction.

To use the lens barrel for image forming apparatuses or optical devicessuch as digital cameras or the like, as described hereinafter, forexample, a solid-state image-sensing device 16 comprising a CCD(Charge-Coupled Device) or the like is disposed adjacent to the side ofan image forming plane of the fourth lens group 14.

Referring to FIG. 9, the first lens group 11 is attached to a firstframe 17, and a cover glass 18 and a low-pass filter 19 are disposedadjacent to an image-receiving surface of the CCD 16, if needed.

Generally, as shown in FIG. 9, the lens barrel is structured such thatthe first to fourth lens groups are movable between a collapsed positionS stored in the fixed cylinder 21 a and an extended position D extendedout of the fixed cylinder 21 a so as to achieve a zooming, and at leastone lens group of the first to fourth lens groups can be retracted outof the optical axis into a retracted position as shown at R in FIG. 9.In the embodiment, at least one portion of the third lens group 13 isretracted from the optical axis passing through a through hole providedin the fixed cylinder 21 a into a stored part provided in the fixedcylinder 21 a and corresponding to the retracted position as describedabove.

Note that any shape or structure may be used instead of the fixedcylinder. For example, a plurality of peripherally spaced slidable barsor bands may be used without being limited to the cylinder shape of thefixed cylinder.

In regard to this, a further detailed description will be describedhereinafter.

The first lens group 11 to the fourth lens group 14 have a zoom lensfunction in which a focal distance is variable, as describedhereinafter. The first lens group 11 includes one or more lens, and isfixed to the lineally-moving cylinder 27 via the first frame 17, whichretains the first lens group 11 integrally.

The second lens group 12 includes one or more lens. A cam followerformed on a second frame (not shown) for integrally retaining the secondlens group 12 is inserted into a cam groove for the second lens group 12formed on the cam cylinder 26 shown in FIGS. 9 and 11, and engages witha linear groove 25 a of the second liner 25, and the second lens group12 is supported by the cam cylinder 26 and the second liner 25.

The shutter/aperture unit 15 includes a shutter and an aperture, and acam follower formed integrally with the shutter/aperture unit 15 isinserted into a cam groove for the shutter/aperture of the cam cylinder26 shown in FIG. 11 and is engaged with the linear groove 25 a on thesecond liner 25 so that the shutter/aperture unit is supported by thecam cylinder 26 and the second liner 25.

The fixed frame 21 includes a cylindrical part having an inner surfacewhich is formed with a linear groove and a helicoidal cam groove alongan axial direction, as shown in FIGS. 13A and 13B. A helicoidal camfollower formed on an outer peripheral surface of a base portion of thefirst rotary cylinder 22 engages with the helicoidal cam groove, asshown in FIG. 13C, and a key portion formed on an inner surface of abase portion of the first liner 23 engages with the linear groove of thefixed frame of the fixed frame 21. An inner surface of the first rotarycylinder 22 is formed with a guide groove extending along a planetransverse to the optical axis X. Engaged with the guide groove is afollower or key which is formed to project from the outer peripheralsurface of the first liner 23 in the vicinity of the base portionthereof and acts as a linear member.

An inner surface of the first liner 23 is formed with a linear groovealong the optical axis. The first liner 23 is also formed with aclearance groove in which a cam follower formed to project from an outerperipheral surface of a base portion of the second rotary cylinder 24 inthe vicinity of the base portion is inserted.

A helicoid is formed on the outer peripheral surface of the base portionof the second rotary cylinder 24, and is engaged with the helicoid ofthe first liner 23. A cam follower formed to project from the outerperipheral surface of the second rotary cylinder 24 in the vicinity ofthe base portion engages with the linear groove formed in the innerperiphery of the first rotary cylinder 22 through the clearance grooveof the cam follower on the first liner 23. A key portion formed toproject from the outer peripheral surface of the base portion of thesecond liner 25 engages with the linear groove provided on the innerperipheral surface of the first liner 23.

An inner surface of the second rotary cylinder 24 is provided with aguide groove along a plane transverse to the optical axis X, a followeror key provided to project from the outer peripheral surface of thesecond liner 25 is engaged in the guide groove of the second rotarycylinder 24. With such a structure, the second liner 25 moves with thesecond rotary cylinder 24 in the movement along the optical axis X,while the second rotary cylinder 24 is rotatable relative to the secondliner 25.

The cam cylinder 26 fitted to the inner periphery of the second liner 25is configured in such a manner that an engaging projection formed on theouter peripheral surface of the base portion is fitted to and engagedwith the base portion of the second rotary cylinder 24 so as to rotateintegrally with the second rotary cylinder 24. The inner surface of thesecond liner 25 is provided with a guide groove along a surfacetransverse to the optical axis X, and a follower or key provided on theouter peripheral surface (front side) of the cam cylinder 26 engageswith the cam groove. With such a structure, the cam cylinder 26 moveswith the second liner 25 in the movement along the optical axis X, whileis rotatable relative to the second liner 25.

The base portion of the lineally-moving cylinder 27 is inserted betweenthe second rotary cylinder 24 and the second liner 25, and a camfollower is formed to project from the outer peripheral surface of thelineally-moving cylinder 27 in the vicinity of the base portion, and thecam follower engages with the cam groove formed in the inner peripheralsurface of the second rotary cylinder 24. A linear groove is formed onthe inner peripheral surface of the lineally-moving cylinder 27 alongthe axial direction, and the key portion formed on the outer peripheralsurface of the second liner 25 engages with the linear groove.

A gear portion is formed on the outer periphery of the base portion ofthe first rotary cylinder 22, the gear portion is engaged with one ormore gears which are driven by a zooming motor 51 so that a drive forceof the zooming motor 51 is transmitted to the gear portion via thegears, whereby the first lens group 11, the second lens group 12, andthe shutter/aperture unit 15 are zoomed in a predetermined manner. Thezooming motor 51 comprises a usual DC motor in the embodiment althoughit is not limited thereto.

Meanwhile, the cam groove on the second rotary cylinder 24 engaging withthe cam follower on the linearly-moving cylinder 27 is shown in FIG. 10.

The cam groove on the cam cylinder 26 which engages with the camfollower on the lens retaining frame of the second lens group 12 and thecam groove of the cam cylinder 26 which engages with the cam follower ofthe shutter/aperture unit 15 are shown in FIG. 11, respectively.

The cam groove on the first liner 23 which engages with the cam followerof the second rotary cylinder 24 and the straight groove on the firstliner 23 which engages with the key groove on the second liner 25 areshown in FIG. 12, respectively.

A linear groove on the fixed frame 21 engaging with the key portion ofthe first liner 23 of the fixed frame and the cam groove of the fixedframe 21 engaging with the cam follower of the first rotary cylinder 22are shown in FIGS. 13A to 13C, respectively.

Generally, the rotary cylinder, which is the closest position to thefixed frame and positioned on the outermost circumference is generallyscrewed onto the fixed frame through a helicoid, and the helicoid isconfigured to move the rotary cylinder at a constant speed relative tothe fixed frame. Therefore, the rotary cylinder is in a half-extendedstate out of the fixed frame in a short focal length/wide angle in acourse in which the rotary cylinder is moved gradually from thecollapsed position through the short focal length/wide angle position toa long-focus/telephoto position.

On the contrary, in the structure described above, the first rotarycylinder 22 adjacent to the fixed frame 21 is threaded with the fixedframe of the fixed frame 21 via the cam groove of the helicoidal shapewithout a simple helicoidal connection. The first rotary cylinder 22 ismoved completely to the maximally extended position by being driven fromthe collapsed position to the short focal length/wide angle position.Thereafter, as shown in FIGS. 13A to 13C, because the subject side endof the cam groove lies in parallel with the end surface of the fixedframe, the first rotary cylinder 22 rotates at a constant positionwithout moving along the optical axis X during driving from the shortfocal length/wide angle position to the long-focus/telephoto position.

In addition, the third lens group 13 is retracted out of the opticalaxis X in the collapsed position, in which the lens groups are collapsedin the fixed frame 21, as shown in FIG. 9. The third lens group 13 ismoved onto the optical axis X in an extended position of the lensgroups.

As the first rotary cylinder 22 is moved from the collapsed position toshort focal length/wide angle position, it is extended toward thesubject, while rotating in an early stage of the extending out actionand when it reach the maximally extended position, a zoomposition-detector which is provided on the fixed frame 21 and comprisinga photo-reflector, photo-interrupter, leaf switch or the like, forexample, generates a zoom position-reference signal. Therefore, when thezoom position-reference signal generates, because it may be determinedthat the first rotary cylinder 22 reaches the maximally extendedposition, it is possible to initiate to move the third frame 31(retractable lens retaining frame according to the present embodiment)onto the optical axis X.

Consequently, a space between the second lens group 12 and the fourthlens group 14 to insert the third lens group 13 into the optical axis Xcan be secured previously by completely extending out the first rotarycylinder 22 and the first liner 23 adjacent to the fixed frame at theearlier step of the extended action.

As described below, as soon as the first rotary cylinder 22 reaches themaximally extended position, the zoom position-reference signalgenerates, the space for inserting the third lens group is secured, andimmediately, the insertion of the third lens group is initiated.Therefore, a time taking to transit from the collapsed state when anelectric source is turned on to the short focal length/wide angle statecan be much shortened.

As described above, the retractable third lens group 13 is retained tothe third frame 31 (retractable lens retaining frame according to thepresent embodiment). The third frame 31 retains the third lens group 13(lens group of the retractable lens retaining frame) at one end thereof,and the other end of the third frame 31 is supported by a third groupmain-guide shaft 32 which extends substantially in parallel with theoptical axis of the third lens group 13 so as to be capable of rotating,and sliding along the third group main-guide shaft 32. The third frame31 is rotatable about the third group main-guide shaft 32 between asetting position (on-optical-axis position or a photographable position)in which the third lens group 13 is disposed onto the optical axis in aphotographing state, as shown in FIG. 8 and the retracted position(collapsed position) in which the third lens group 13 is retracted outof the telescopic cylinder (retracted state) (alternatively, retractedout of the fixed cylinder 21 a into the fixed frame 21), as shown inFIG. 2.

In the vicinity of the third lens group 13 on the side of the rotatingend of the third frame 31, a crank-shaped bent portion fordifferentiating the position of the third lens group 13 in the directionparallel with the main guide shaft between the side of the rotation axisand the side of the supporting portion, a stopper 31 a (FIGS. 15A and15B) and a light-shielding member 31 b are provided on the rotating endto project from the bent portion substantially toward the rotating end.

The light-shielding member 31 b is configured to be detected by athird-frame photo-interrupter 38 when the third frame 31 is in theretracted position. Thereby, it is possible to detect that the thirdlens group 13 (the retractable lens retaining frame according to thepresent embodiment) is in the retracted state.

On the optical performance, in order to lengthen a focus length in thetelephoto state, a position of the third lens group 13 in the telephotostate is in an extended position closer to the subject. However, apossible moving amount of the third frame 31 is determined by limitationof a length of the lens barrel in the collapsed state along the opticalaxis X. It is possible to maximize the focus length in the telephotostate by setting a position for retaining the third lens group by thethird frame 31 in the closest position to the subject. However, if aposition of the stopper 31 a along the optical axis sets on thegenerally same position as the third lens group 13, a length of a thirdframe sub-guide shaft 33 is longer and a size of the lens barrel in thecollapsed state becomes greater. Therefore, it is required that thestopper 31 a is set on a side of a focusing position and the third frame31 is formed into a shape having the crank-shaped bent portion.

Meanwhile, the third frame 31 may be formed from two parts and in thiscase, one is a member having the crank-shaped bent portion, and theother is a member for retaining the third lens group 13. The two partsoperates integrally by being fixed together.

As shown in FIGS. 14A and 14B, a third frame female screw member 35screwed on a third group lead screw 34 is positioned in the closestposition to an image plane of the CCD in the retracted state in whichthe third frame 31 is retracted. In this state, as shown in FIGS. 15Aand 15B, a compression torsion spring 37 is charged or compressed fullyso as to impart constantly a clockwise moment M1 (a direction enteringtoward the optical axis, see FIG. 15A) to the third frame 31 as viewedfrom the front of the lens barrel, and also so as to press the thirdframe 31 toward a retainer plate 81.

A cylindrical outer peripheral surface of a supported part provided onthe main-guide shaft 32 for the third frame 31 is provided with astepped portion 31 c, and a cam portion 31 e (cam groove) disposedinside the stepped portion 31 c and formed from an inclined surface, asshown in FIG. 14A.

From this state, when a third frame drive motor 52 is rotated clockwiseas viewed from the front of the lens barrel, the third group lead screw34 is rotated clockwise through a gear mechanism including gears 71 to74, and the third frame female screw member 35 moves toward the subjectalong the optical axis X. At this time, the third frame 31 is rotatedclockwise by the moment force M1 of the compression torsion spring 37,and the cam portion 31 e engages with a protruded abutting portion(contact portion) 35 c provided on the third frame female screw member35. Because of the twisting force of the compression torsion spring 37,the cam portion 31 e constantly contacts with the abutting portion 35 cof the third frame female screw member 35. In other words, one end ofthe compression torsion spring 37 is supported by the fixed frame 21 andthe other end of the compression torsion spring 37 contacts with aprotrusion 31 h of the third frame 31 to bias the third frame 31, andthereby, the cam portion 31 e constantly contacts with the abuttingportion 35 c of the third frame female screw member 35.

As shown in FIGS. 33A and 33B, a part of the cam portion 31 e near tothe gear 74 is slanted and a part of the cam portion 31 e facing towarda side of the subject is formed to be perpendicular to the lead screw34. The third frame 31 is in the retracted state when the abuttingportion 35 c is located at a position closest to the gear 74. When theabutting portion 35 c draws away from the gear 74, the slanted part ofthe cam portion 31 e is supported by the abutting portion 35 c and thethird frame 31 starts to rotate by the twisting force of the compressiontorsion spring 37. The third frame 31 is located in the photographablestate when the abutting portion 35 c enters into an inner portion (backportion) 31 g of the cam portion 31 e, and thereby the optical axis ofthe third lens group 13 of the third frame 31 coincides with otheroptical axes of the first lens group 11, the second lens group 12 andthe fourth lens group 14. When the lead screw 34 is further rotated, theabutting portion 35 c pushes a front engaging portion 31 d of the camportion 31 e toward the subject so that the third frame 31 moves towardthe subject.

Thereafter, when the third frame female screw member 35 is moved in theclosest position to the subject by the rotation of the lead screw 34,the light-shielding member 31 b of the third frame 31 is moved to aposition out of the third frame photo-interrupter 38 as a device fordetecting a position of the third lens group 13 (third lens groupposition detecting device), thereby the third frame photo-interrupter 38generates a reference signal in a range from L (or a low) level to H (ora high) level. Accordingly, a position of the third lens group 13 iscontrolled by pulse count based on the reference signal from the thirdframe photo-interrupter 38.

From this state, when the third frame female screw member 35 is moved toa retract-initiating position B of the third frame 31, as shown in FIG.14A, the third frame 31 further rotates clockwise, and the stopper 31 acomes into abutment with the third frame sub-guide shaft 33 as shown inFIGS. 8 and 16A. As a result, a position of the third frame 31 on theoptical axis (the on-optical-axis position) is determined. Consequently,approach operation of the third lens group 13 to the optical axis iscompleted. In the retract-initiating position B, the third frame 31 ismovable toward the retracted position S.

Meanwhile, the light-shielding member 31 b shields the third framephoto-interrupter 38 shown in FIG. 16A so that it is possible to detectand confirm that the third frame 31 is in the retracted position S orthe retract-initiating position B. When the third frame female screwmember 35 is moved to the retract-initiating position B shown in FIG.14A, the abutting portion 35 c of the third frame female screw member 35contacts with the front engaging portion 31 d of the stepped portion 31c of the third frame 31. Again, the stepped portion 31 c of the thirdframe 31 has the cam portion 31 e which forms a slanted shape on a baseend side and the front engaging portion 31 d which forms a plannersurface generally perpendicular to the third group main guide shaft 32on a front end side thereof.

The third frame 31 is constantly biased to move to a directiontransverse to the optical axis, i.e., from the retracted position to theoptical axis (or to the on-optical-axis position) as well as to adirection along the optical axis, i.e., from the subject to a retainerplate 81 beside the image plane by the compression torsion spring 37provided on the third group main-guide shaft 32.

The third frame female screw member 35 is formed with a T-shapedprotruded member 350 as a portion to be detected (detected portion) atan opposite side of a rotation-preventing projection 35 b which slidesin a guide groove G1 as shown in FIG. 15A. The T-shaped protruded member350 has a substantially alphabet “T” configuration. A vertical lineportion located at the center of the alphabet “T” configuration of theT-shaped protruded member 350 is attached to the third frame femalescrew member 35, whereas a horizontal line portion of the alphabet “T”configuration thereof extends in directions to which the third framefemale screw member 35 moves (i.e. an axial direction of the lead screw34).

The T-shaped protruded member 350 and a transmissive photo-interrupter351 structure a position detector. The position detector is configuredto detect the retracted position in the retracted state of the thirdframe 31, a position of the third frame 31 on the optical axis X at thetime when the entering of the third frame 31 from the retracted positiononto the optical axis X has completed in the transition from theretracted state to the photographable state (hereinafter simply referredto as an optical axis entrance completed position), and a distance froma reference position of the third frame 31 or a position of the thirdframe 31 in the photographable state wherein the focal distance duringthe wide-angle photographing and the telephoto photographing is changed.Here, an output of the photo-interrupter 351 is outputted to acontroller such as a central calculation processing device 501 whichwill be described later, and the power of the photo-interrupter 351 issupplied from a power source of the camera.

The photo-interrupter 351 is installed near a position within an areathat the horizontal line portion of the T-shaped protruded member 350moves and where the third frame female screw member 35 stands by in apart near to the gear 74 of the lead screw 34 as a home position. Thephoto-interrupter 351 is installed such that the photo-interrupter 351once outputs an output of an H level, then outputs an output of an Llevel, and then outputs the H level output again thereafter, when thethird frame female screw member 35 moves from the home position towardthe axial direction of the lead screw 34, or when the third frame femalescrew member 35 returns to the stand by position as the home positionfrom a position distant from the home position.

As shown in FIG. 34, the photo-interrupter 351 outputs the L-leveloutput when the T-shaped protruded member 350 enters between alight-emitting device and a light-receiving device of thephoto-interrupter 351 and thus the T-shaped protruded member 350 shieldstherebetween. The photo-interrupter 351 outputs the H-level output whenthe T-shaped protruded member 350 does not exist between thelight-emitting device and the light-receiving device of thephoto-interrupter 351 and thus the light-receiving device receives thelight.

More specifically, the position where the photo-interrupter 351 islocated is so set that the T-shaped protruded member 350 of the thirdframe female screw member 35 is out from the photo-interrupter 351 whenthe T-shaped protruded member 350 is positioned nearest to the gear 74and thus the H-level output is outputted. Such a location of theinstalled position of the photo-interrupter 351 is for the purpose ofchanging the output of the photo-interrupter 351 from “H” to “L” to “H”at the time that the third frame female screw member 35 passes throughthe photo-interrupter 351 when the third frame female screw member 35moves from the telephoto to the gear 74 toward the gear 74 to approachutmost to the gear 74, so as to detect that the third frame female screwmember 35 has passed though the photo interrupter 351 (or passed betweenthe light-emitting device and the light-receiving device).

The home position of the third frame female screw member 35 is aposition where a predetermined time has elapsed from a falling edge ofthe L-level output (after the predetermined number of pulses is counted)when the third frame female screw member 35 moves from the positionnearest to the gear 74 toward the subject side and thus the output ofthe photo-interrupter 351 changes from “H” to “L” to “H”, as shown inFIG. 34. Such a position where the predetermined amount of time haselapsed from the falling edge of the L-level output is defined as areference position of the home position.

Thereby, it is possible to determine reference positions for judging anamount of movement of the third frame female screw member 35, and henceit is possible to detect that the third frame 31 is in the state ofbeing positioned at the retracted position. In addition, similarly, itis possible to detect that the third frame 31 is at the optical axisentrance completed position based on elapsing of a predetermined amountof time from a rising edge of the output (before the predeterminednumber of pulses is counted) when the output of the photo-interrupter351 rises from the “L” to “H” (a reference position of the optical axisentrance completed position).

Because the reference position for the home position and the opticalaxis entrance completed position are revealed accurately, it is possibleto judge a wide angle photographing position and a telephotophotographing position accurately according to, for example but notlimited to, multiplication of the number of rotations and a feedingpitch of the lead screw 34 from the reference position.

More specifically, although the photo-interrupter 351 is shielded by thehorizontal line portion of the T-shaped protruded member 350 of thethird frame female screw member 35, it is uncertain which part of thehorizontal line portion of the T-shaped protruded member 350 ispositioned between the light-emitting device and the light-receivingdevice of the photo-interrupter 351 when the output of thephoto-interrupter 351 is the “L” level, since the horizontal lineportion of the T-shaped protruded member 350 itself has a certain lengthin the moving direction thereof. Also, even if the photo-interrupter 351is able to specify a point of time that the output of thephoto-interrupter 351 falls from the “H” to “L”, or a point of time thatthe output rises from the “L” to “H”, it is difficult to grasp anaccurate position of the third frame 31 due to inertia of the motor, thegear mechanism and so on, or a variation in precision of the mechanismfor example.

Therefore, a position of the third frame 31, where the third frame 31 islocated before a predetermined time elapses from the time when theoutput of the photo-interrupter 351 has fallen from “H” to “L” and risenfrom the “L” to “H” again, when the third frame 31 returns to the homeposition from the position distant from the home position, is defined asthe home position. In other words, the home position is the point oftime that the output falls from the “H” to “L” and the predeterminedtime has elapsed therefrom when the third frame female screw member 35moves from the stand by position toward the subject side.

Accordingly, when the third frame female screw member 35 moves from thestand by state position toward the subject side again and thus theoutput of the photo-interrupter 351 changes from the “H” to “L” to “H”,it is possible to detect that the third frame female screw member 35 haspassed the home position by the detection of the predetermined number ofpulses from the falling edge of the “L” level output signal. Thepredetermined number of pulses from the falling edge of the “L” leveloutput signal to the detection of the predetermined number of pulses isfor example determined by measurement of the focal positions of theactual lens barrel or by calculation.

FIG. 35 shows the alternative detected portion. Here, the detectedportion detected by the photo-interrupter 351 is an L-shaped protrudedmember 352 having a substantially alphabet “L” configuration. As similarto the case of the T-shaped protruded member 350 shown in FIG. 34, theinstalled position of the photo-interrupter 351 is so located that theL-shaped protruded member 352 of the third frame female screw member 35is out of the photo-interrupter 351 when the L-shaped protruded member352 is positioned nearest to the gear 74 and thus the H-level output isoutputted.

Such a location of the installed position of the photo-interrupter 351is for the purpose of changing the output of the photo-interrupter 351from the “H” to “L” to “H” by making the third frame female screw member35 to pass through the photo-interrupter 351 when the third frame femalescrew member 35 moves from the telephoto toward the gear 74 to approachutmost to the gear 74, so as to detect that the third frame female screwmember 35 has passed though the photo interrupter 351 (or passed betweenthe light-emitting device and the light-receiving device).

Thereby, it is possible to judge that the third frame 31 is in the stateof being positioned at the retracted position. Also, it is possible tojudge that the third frame 31 is at the optical axis entrance completedposition. Additionally, because the reference positions for the homeposition and the optical axis entrance completed position are judgedaccurately, it is possible to determine the wide angle photographingposition and the telephoto photographing position accurately accordingto, for example but not limited to, the multiplication of the number ofrotations and the feeding pitch of the lead screw from the referenceposition.

Since operation of the L-shaped protruded member 352 of the third framefemale screw member 35 is similar to that of the T-shaped protrudedmember 350 and the definition of the home position of the third framefemale screw member 35 utilizing the rising edge and the falling edge ofthe output from the photo-interrupter 351 is similar as well, they arenot described in detail.

Here, it is to be noted that the configuration of the detected portionof the third frame female screw member 35 detected by thephoto-interrupter 351 is not limited to the alphabet “T” or “L”configuration. Other configuration or shape may be employed as long assimilar effect described above is obtained by such a shape orconfiguration.

In addition, a portion of the fixed frame 21 to which the compressiontorsion spring 37 contacts includes a step 37 a which is formed as aconcave portion for inserting one end of the compression torsion spring37 as shown in FIG. 14B, to prevent the compression torsion spring 37from deviating out of a center of the third group main-guide shaft 32considerably.

Next, when the third frame female screw member 35 is moved to a shortfocal length/wide angle position (the wide angle position W shown inFIG. 14A), because the abutting portion 35 c of the third frame femalescrew member 35 presses the front engaging portion 31 d, the third frame31 is movable to the wide angle position along the optical axis X towardthe subject.

Moreover, while the third frame female screw member 35 is disposedbetween the retract-initiating position B and the telephoto position Tas shown in FIG. 14A, because the third frame 31 is constantly pressedalong the optical axis toward the image plane by the compression torsionspring 37, all spaces generated among the third group lead screw 34, thethird frame female screw member 35 and the retainer plate 81 aredirected to the image plane, so that the third frame 31 can secure apositional accuracy in the direction of the optical axis.

The third frame female screw member 35 is screwed on the third grouplead screw 34 disposed substantially in parallel with the optical axis.The third frame female screw member 35 includes the rotation-preventingprojection 35 b in addition to the abutting portion 35 c, which engageswith the above-described front engaging portion 31 d or the cam portion31 e of the third frame 31.

The rotation-preventing projection 35 b is fitted slidably into theguide groove G1 (see FIG. 15A) formed on the cylindrical part of thefixed frame 21 in parallel with the optical axis as arotation-preventing device for preventing the third frame female screwmember 35 from rotating along with the rotation of the third lead screw34, as shown in FIGS. 15A and 15B. In other words, the third framefemale screw member 35 is moved in the back and forth directions alongthe optical axis by the rotation of the third lead screw 34, because thethird frame female screw member 35 is prevented from rotating by therotation-preventing projection 35 b fitting into the guide groove G1 ofthe fixed frame 21.

As shown in FIG. 14A in detail, when the third frame female screw member35 is moved further toward the image plane (left side in the drawing)from the retract-initiating position B shown in FIG. 14A, the thirdframe female screw member 35 engages with the cam portion 31 e of thestepped portion 31 c of the third lens group-retaining frame 31.

The third frame 31 comes into contact with the retainer plate 81 by thebiasing force of the compression torsion spring 37 toward the opticalaxis X direction, and the third frame 31 is rotated counterclockwiseagainst the clockwise biasing force exerted by the compression torsionspring 37. Therefore, it is possible to retract the third frame 31.

On the other hand, while the third frame female screw member 35 is movedfrom the telephoto position T through the wide angle position W to theretract-initiating position B by the reverse rotation orcounterclockwise rotation of the third group lead screw 34, because theabutting portion 35 c of the third frame female screw member 35 engageswith the front engaging portion 31 d of the stepped portion 31 c of thethird frame 31, the third frame 31 moves gradually to direct from thesubject to the image plane while maintaining the position on the opticalaxis (on-optical-axis position) restricted by the third frame sub-guideshaft 33 by the biasing force toward the optical axis and the biasingforce toward the image plane.

Meanwhile, when the third frame female screw member 35 reaches theretract-initiating position B, a base end surface 31 f contacts with theretainer plate 81, and the third frame female screw member 35 isdisposed with an interval from the front engaging portion 31 d, andcontacts with the cam portion 31 e of the stepped portion 31 c.

While the third frame female screw member 35 moves from theretract-initiating position B to the collapsed position S, the abuttingportion 35 c of the third frame female screw member 35 comes intosliding contact with the cam portion 31 e of the stepped portion 31 c ofthe third frame 31 and rotates the third frame 31 against the rotationalbiasing force exerted by the compression torsion spring 37, whereby thethird frame 31 moves from the position on the optical axis to thecollapsed position S. The collapsed position S of the third frame 31corresponds to a position at which it is moved toward the image plane bya predetermined pulse count number after the generation of the referencesignal of the range from the H to the L generated from the third framephoto-interrupter 38. After the third frame 31 is moved to the collapsedposition S, the first lens group 11, the second lens group 12, and theshutter/aperture unit 15 are moved to the collapsed position.

In this example, before the third frame 31 is moved to the collapsedposition S, a fourth frame 41 for retaining the fourth lens group 14 isfirst moved to the collapsed position. A first collapsed position of thefourth frame 41 corresponds to a position at which it is moved towardthe image plane by a predetermined pulse count number after thegeneration of a storage reference signal of a range from the H to the Lgenerated by a fourth group reference detector (fourth groupphoto-interrupter 47). After the fourth frame 41 reaches the firstcollapsed position, the stored operation of the third frame 31 isinitiated.

That is to say, the third frame female screw member 35 moves toward theimage plane by a predetermined pulse count number from the generation ofthe stored reference signal from the H to the L by the third framephoto-interrupter 38 (see FIG. 16A), and the stored operation of thethird frame 31 completes. After the completion of the stored operationof the third frame 31, the first rotary cylinder 22 and structural partsdisposed inside the first rotary cylinder 22 and the first liner 23 andso on are stored before contacting with the third frame 31. This resultsin the storage of the first rotary cylinder 22 and so on withoutinterfering with the third frame 31.

Positions of the first rotary cylinder 22 and so on can be set by adrive pulse count generated by a zoom count detector comprising a piniongear attached directly to an output shaft of the zooming motor 51 andhaving an encoder structure and a first and second framesphoto-interrupter 51 a disposed adjacent the pinion gear, for example.

Meanwhile, although the DC motor is used as the drive source for movingthe first rotary cylinder 22 and the drive position of the first rotarycylinder 22 is detected by the detector comprising the encoder and thephoto-interrupter, in the above-mentioned example, the similar functioncan be accomplished by substituting a pulse motor structure for thewhole of the above-mentioned structure.

To prevent the third frame 31 from collision with the other parts, animpact-preventing member 36 is, as shown in particular in FIGS. 2 and 7,rotatably supported on the fixed frame 21 in the vicinity of the thirdgroup main-guide shaft 32, and includes a rotated portion provided atone end of the impact-preventing member 36 and an engaging projection 36a. The impact-preventing member 36 is constantly biased to cause theengaging projection 36 a to move toward the optical axis X by a springor the like.

When the third frame 31 is positioned in the collapsed position, theimpact-preventing member 36 is pushed out by rotating force of the thirdframe 31 against biasing force of the spring, and is deviated outsidethe third frame 31 (see particularly FIG. 2 and FIG. 7).

When the third frame 31 is rotated and positioned on the optical axis(on-optical-axis position), the impact-preventing member 36 is releasedfrom engagement with the third frame 31, and is rotated to cause theengaging projection 36 a to be projected toward the optical axis X bythe biasing force, thereby causing the engaging projection 36 a toproject from the inner surface of the fixed cylinder 21 a of the fixedframe 21. At this time, in addition to the first rotary cylinder 22 andthe first liner 23, the second rotary cylinder 24, the second liner 25,the cam cylinder 26 and the lineally-moving cylinder 27 are allpositioned on the subject side with respect to the projected position ofthe engaging projection 36 a. Therefore, the engaging projection 36 a ispositioned to project inwardly of an outer peripheral edge of the baseportion of each of the first rotary cylinder 22 and the first liner 23(see particularly FIG. 5, FIG. 6, and FIG. 8).

With such a structure, even if an operator tries to manually rotate thefirst rotary cylinder 22 forcibly so as to move it to the collapsedposition, the impact-preventing member 36 first contacts with the firstrotary cylinder 22. Therefore, because the base portion of the firstrotary cylinder 22 cannot be moved toward the image plane than theposition of the impact-preventing member 36 along the optical axis, thefirst rotary cylinder 22 is prevented from contacting with the thirdframe 31. Accordingly, it is possible to accomplish the prevention ofbreaking, damage or the like of the third frame 31 due to strongexternal force. Here, the first rotary cylinder 22 can be moved to thecollapsed position only after the third frame 31 is moved to thecollapsed position correctly.

Therefore, in a state of being used or in the photographing state of thelens barrel, in which the movable cylinders such as the first rotarycylinder 22 and so on are extended, when a great pressure is exerted ona leading end of the lens barrel and so on by a drop of the lens barrelor the like, the engaging projection 36 a of the impact-preventingmember 36 engages with the first rotary cylinder 22 and the first liner23, and hence further retraction of the first rotary cylinder 22 and thefirst liner 23 (as well as the second rotary cylinder 24, the secondliner 25, the cam cylinder 26, and the lineally-moving cylinder 27)toward the third lens group 13 is prevented. Accordingly, the thirdframe 31 and the third lens group 13 are prevented from being damaged.

The third group lead screw 34 is rotated in forward and reversedirections by a third frame drive motor 52. The rotation of the thirdframe drive motor 52 is transmitted to the third group lead screw 34 viagears 71, 72, 73, and 74 arranged in sequence.

Next, a drive structure of the fourth lens group 14 is described withreference to FIGS. 7, 8, 20A and 20B. Note that each of the FIGS. 20Aand 20B is a perspective view mainly showing a drive system of thefourth lens group 14.

The fourth lens group 14 comprising at least one optical element (forexample but not limited to, a lens) is located nearer to the image planeof the CCD than the third frame 31. The position detector structured bythe photo-interrupter 351 and the T-shaped protruded member 350 or theL-shaped protruded member 352 generates a signal indicating that theentering of the third frame 31 into the optical axis X has completedwhen the state of the retractable lens retaining frame has changed fromthe collapsed state to the photographable state, and thereafter, permitsthe movement of the fourth lens group 14.

The fourth lens group 14 used as a focusing lens for focusing the lensgroups in the illustrated embodiment is retained by the fourth frame 41,as shown in FIGS. 20A and 20B. The fourth frame 41 includes a sleeveportion 41 a in which a fourth frame main-guide shaft 44 disposed inparallel with the optical axis and fixed to a lens barrel base 82 isfitted, and a rotation-preventing portion 41 b in which a fourth framesub-guide shaft 42 disposed in parallel with the optical axis and fixedto the lens barrel base 82 is fitted, to restrict the rotation of thefourth frame 41. With such a structure, the fourth frame 41 can be movedfreely along the fourth frame main-guide shaft 44, i.e. the opticalaxis. A fourth frame drive motor 53 comprising a stepping motor is usedas a drive source for driving the fourth frame 41 in the illustratedembodiment. Provided on an output shaft of the fourth frame drive motor53 is a fourth frame lead screw 45 which is threaded into a threadedhole provided in a fourth frame female screw member 46.

The fourth frame 41 has an opening for inserting the fourth frame femalescrew member 46. The opening has an engaging portion 41 c for engagingwith the fourth frame female screw member 46 in a perpendicular plane tothe optical axis in a side of the image plane. The fourth frame 41 isalways engaged with the fourth frame female screw member 46 by allowingthe fourth frame 41 to bias toward the subject by a fourth frame spring43.

The fourth frame female screw member 46 has a radially projectedprotrusion 46 a. The protrusion 46 a is engaged in a bore 41 d providedin one side of the opening for inserting the fourth frame female screwmember 46 of the fourth frame 41 so that the rotation of the fourthframe female screw member 46 is stopped.

In this way, when the fourth frame drive motor 53 which is the steppingmotor for example is driven, the fourth frame lead screw 45 rotates, andhence, the fourth frame female screw member 46 is moved in the forwardand reverse directions along an axis of the fourth frame lead screw 45(i.e. the optical axis X). Because the fourth frame 41 engages with thefourth frame female screw member 46, the fourth frame 41 is moved alongthe optical axis following to the movement of the fourth frame femalescrew member 46. In this case, although the fourth frame lead screw 45is formed on the output shaft of the fourth frame drive motor 53, thefourth frame lead screw 45 may be rotated by structuring the fourthframe drive motor 53 and the fourth frame lead screw 45 separately andconnecting them through gears or the like.

The fourth frame 41 is provided with a light-shielding piece 41 e whichshields an optical passage of a fourth group photo-interrupter 47provided on the lens barrel base 82. The light-shielding piece 41 e iscapable of light-shielding or passing light through the optical passageof the fourth group photo-interrupter 47 in response to the movement ofthe fourth frame 41. In this case, the fourth frame 41 can be moved in apredetermined position by recognizing as a reference position a time atwhich the light-shielding pieces is set from the light-shielding stateto the light-passing state and energizing a pulse waveform of any pulsenumber from the reference position to rotate the fourth frame drivemotor 53.

Meanwhile, the fourth frame 41 has a concave portion 41 f which isprovided in an outer peripheral edge thereof and allows thelight-shielding member 31 b of the third frame 31 for thephoto-interrupter 38 to move toward the optical axis to avoid theinterference with the fourth frame 41, thereby the movement amount ofthe fourth frame 41 can be increased and a range capable of focusing canbe enlarged. Moreover, as described above, there is a clearance betweenthe fourth frame 41 and the fourth frame female screw member 46 in thedirection of the optical axis, but the position in the direction of theoptical axis of the fourth frame 41 can be controlled accurately byconstantly biasing the fourth frame 41 toward the subject by the fourthframe spring 43.

The collapsed position of the first rotary cylinder 22, the first liner23, the first lens group 11, the second lens group 12, and theshutter/aperture unit 15 is controlled based on the zoomposition-reference signal generated by the zoom position detectorcomprising the photo-reflector and so on disposed in the fixed frame 21.That is to say, it is possible to complete the storing operation bymoving them toward the image plane by the predetermined pulse countnumber of the drive pulse generated by the pinion gear acting as theencoder and the zoom count detector disposed adjacent to the pinion gearafter the change of from the H to the L of the zoom position storagereference signal occurs.

In storing, the fourth frame 41 is positioned in the first collapsedposition as described above, while, when the first rotary cylinder 22 ismoved to the collapsed position, the most distal surface of the firstrotary cylinder 22 or the first liner 23 contacts with the fourth frame41 and presses the fourth frame 41 to move to the second collapsedposition finally.

By such an operation, even if variations of the attached position of thefourth group photo-interrupter 47 in the direction of the optical axisoccur, the fourth frame 41 can be moved to the collapsed positionaccurately without requiring a complicated adjustment. Such an operationcan be accomplished for the reason that a length of the engaging spaceformed in the fourth frame 41, in the direction of the optical axis islarger than a thickness of the fourth frame female screw member 46.

The zooming motor 51 for moving the first lens group 11, the second lensgroup 12, and the shutter/aperture unit 15 is structured by the DC motorfor example as described above in the illustrated embodiment. The thirdframe drive motor 52 for driving the third lens group 13 and the fourthframe drive motor 53 for driving the fourth lens group 14 are generallyconfigured to use a pulse motor for example. The zooming motor 51, thethird frame drive motor 52 and the fourth frame drive motor 53 aredriven in conjunction with each other in a software-like manner toachieve an appropriate zooming action performed mainly by the first tothe third lens groups 11-13 and an appropriate focusing action performedmainly by the fourth lens group 14, for example.

Now, a drive control system for the lens groups structuring the lensbarrel is described in detail with reference to FIGS. 21 to 28.

The drive control system is shown in FIG. 21. The drive control systemincludes the central calculation processing device 501, a motor driver502, a first and second frames DC motor 503, a first aperture stop motor504, a second aperture stop motor 505, a shutter motor 506, a thirdframe pulse motor 507, a fourth frame pulse motor 508, a first andsecond frames photo-interrupter 509, a first and second framesphoto-reflector 510, the third frame photo-interrupter 351 (the thirdframe photo-interrupter 351 and the T-shaped protruded member 350 or theL-shaped protruded member 352 structure the position detector for thedetection of the location of the third frame 31), a fourth framephoto-interrupter 512, a first and second frames photo-interrupter drivecircuit 513, a first and second frames photo-reflector drive circuit514, a third frame photo-interrupter drive circuit 515, and a fourthframe photo-interrupter drive circuit 516.

The central calculation processing device 501 gives a command such as aninitial setting of the motor driver 502, the selection for a drivemotor, the setting of a drive voltage, a direction for driving and soon, to the motor driver 502. The motor driver 502 controls the motorsystem of the first and second frames DC motor 503, the first aperturestop motor 504, the second aperture stop motor 505, the shutter motor506, the third frame pulse motor 507, the fourth frame pulse motor 508and so on, in accordance with the command from the central calculationprocessing device 501.

The first and second frames DC motor 503 drives the first and secondlens groups 11 and 12. As always, the first and second groups 11 and 12are driven separately with respect to each other through a cam mechanismin response to the drive of the first and second frames DC motor 503.The first aperture stop motor 504 and the second aperture stop motor 505are configured to drive an aperture stop of the shutter/aperture unit15. The shutter motor 506 drives a shutter of the shutter/aperture unit15. The third frame pulse motor 507 drives the third lens group 13. Thefourth frame pulse motor 508 drives the fourth lens group 14.

The central calculation processing device 501 supplies a driveelectricity to the first and second frames photo-interrupter 509, thefirst and second frames photo-reflector 510, the third framephoto-interrupter 351 (structures the position detector with theT-shaped protruded member 350 or the L-shaped protruded member 352), andthe fourth frame photo-interrupter 512 as the device for detectingposition through the first and second frames photo-interrupter drivecircuit 513, the first and second frames photo-reflector drive circuit514, the third frame photo-interrupter drive circuit 515, and the fourthframe photo-interrupter drive circuit 516. The central calculationprocessing device 501 also acquires a positional information signaldetected by the first and second frames photo-interrupter 509, the firstand second frames photo-reflector 510, the third frame photo-interrupter351, and the fourth frame photo-interrupter 512.

The first and second frames photo-interrupter drive circuit 513, thefirst and second frames photo-reflector drive circuit 514, the thirdframe photo-interrupter drive circuit 515, and the fourth framephoto-interrupter drive circuit 516 have a function to control suitablya level of a projecting current and an output signal of each of thefirst and second frames photo-interrupter 509, the first and secondframes photo-reflector 510, the third frame photo-interrupter 351, andthe fourth frame photo-interrupter 512.

The motor driver 502 receives a command from the central calculationprocessing device 501 and executes the command. The central calculationprocessing device 501 sets a designated voltage to one or more selectedmotors of the first and second frames DC motor 503, the first aperturestop motor 504, the second aperture stop motor 505, the shutter motor506, the third frame pulse motor 507, the fourth frame pulse motor 508,and controls them in accordance with a timing of drive command.

Here, a lens barrier 62 for protecting the lens barrel is described asfollows.

The lens barrier 62 shown in FIG. 3 to FIG. 5 is disposed to cover aside of the first lens group 11 facing the subject, in the stored state,and protects the lens group from contaminations or damages. The lensbarrier 62 is moved in back and forth directions transverse to theoptical axis by a barrier drive system 63. FIGS. 3 and 4 show a state inwhich the lens barrier 62 is closed, and FIG. 5 shows a state in whichthe lens barrier 62 is almost opened. The barrier drive system 63 drivesthe lens barrier 62 between the closed position (FIGS. 3 and 4) and theopened position (a position farther from the optical axis than theposition shown in FIG. 5) through the operation of a barrier-operatingelement (see a barrier-operating element 301 in FIG. 17A). The barrierdrive system 63 has a function to bias the lens barrier 62 in a closingdirection at the closed position and in an opening direction at theopened position.

Therefore, when driving the lens barrier 62 in the closed state towardthe opening direction, the lens barrier 62 is moved to the opened statesemi-automatically when the lens barrier 62 passes a predeterminedposition. Also, when an attempt is made to close the lens barrier 62from the opened state, the lens barrier 62 is moved to the closed statesemi-automatically when the lens barrier 62 passes a predeterminedposition. The position in the closed state is not necessarily requiredto be the same as the predetermined position in the opened state;rather, it is preferable that the lens barrier has a certain degree ofhysteresis characteristics in the movement to accomplish a smoothoperation of the lens barrier 62.

A barrier control member 61 is provided on a side of the fixed frame 21in the direction of opening the lens barrier 62 so as to be capable ofsliding in a direction along the optical axis, and is biased toward thesubject by a spring or the like as needed. In the stored state, anengaging portion of the barrier control member 61 which is formed into abent shape engages with base edge surfaces of the first rotary cylinder22 and the first liner 23 and is biased toward the image surface againstbiasing force of the spring, and hence is not in contact with the lensbarrier 62. In the used or photographing state, the lens barrier 62 iscompletely away from the respective lens groups and retaining framesthereof. In this state, engagement of the engaging portion of thebarrier control member 61 is released, and hence the barrier controlmember 61 is biased toward the subject by the biasing force, and then, abarrier-intercepting portion at the distal end enters into a passage ofthe lens barrier 62.

In this state, when the lens barrier 62 is rapidly operated to move thelens barrel to the collapsed position, there is a possibility that thelens barrier 62 hits against the lens barrel. However, since thebarrier-intercepting portion at the distal end of the barrier controlmember 61 crosses the passage of the lens barrier 62, the lens barrier62 is prevented from entering into a moving passage of the lens barrel.When the respective lens groups are stored and the stored state iscompleted, the base edge surfaces of the first rotary cylinder 22 andthe first liner 23 engage with the engaging portion of the barriercontrol member 61, which is formed into the bent shape, to energize theengaging portion toward the image surface against the biasing force.Therefore, the lens barrier 62 can be moved to the front portion of thelens barrel, and hence the lens barrier 62 is correctly set to theclosed position. In this manner, the interference between the lensbarrier 62 and the lens cylinders retaining the lens groups can beeffectively prevented.

<Activation Sequence>

An activation sequence of the above-mentioned drive control system isexplained with reference to FIG. 22.

By opening the lens barrier 62, a barrier switch signal (barrier SW)from a barrier switch (not shown) changes from the H to the L and aninitial setting of the lens barrel is initiated. Meanwhile, the barrierswitch is operated by opening mechanically the lens barrier 62 with anoperating lever or the like (not shown), while the lens barrier may beopened by operation of the barrier switch. Executing of the initialsetting causes the initialization of the motor driver 502 for drivingthe motor system, and also causes the initialization of the first andsecond frames photo-interrupter 509, the first and second framesphoto-reflector 510, the third frame photo-interrupter 351 (positiondetector), and the fourth frame photo-interrupter 512, as the positiondetecting devices which detect positions through the first and secondframes photo-interrupter drive circuit 513, the first and second framesphoto-reflector drive circuit 514, the third frame photo-interrupterdrive circuit 515, and the fourth frame photo-interrupter drive circuit516.

In the case that detected results by the first and second framesphoto-interrupter 509, the third frame photo-interrupter 351, and thefourth frame photo-interrupter 512 indicate the collapsed position, thefirst and second frames DC motor 503 is adapted to be driven toward thewide angle position. A driven amount of the first and second frames DCmotor 503 is detected by the first and second frames photo-interrupter509 for detecting the moving amount of the first and second lens groups.The moving amount is detected by counting edge portions of the pulsesignal (PI signal) by the first and second frames photo-interrupter 509.

During an activation period immediately after the first and secondframes DC motor 503 is activated, the drive voltage is set to be lowerthan a constant voltage so as to prevent a rush current by the DC motor.After the activation period is completed, the drive voltage is increasedto a stationary voltage.

A period for monitoring the barrier switch (barrier SW) immediatelyafter the initiation of the activation of the first and second frames DCmotor 503 is set and a state of the barrier switch signal is monitoredby the central calculation processing device 501. During the monitoringperiod, if the barrier switch signal indicates the opening state of thelens barrier, the shutter is set in the full opening by the shuttermotor 50 for driving the shutter. Then, the aperture stop is set in anintermediately restricted state by the first and second aperture stopmotors 504 and 505. In this example, although the aperture stop is setin the intermediately restricted state, the aperture stop may be set inan opened state (fully opened state).

Subsequently, the fourth lens group 14 is previously driven through thefourth pulse motor 508. By achieving the previous drive of the fourthlens group 14, the total time from the initiation of the drive of thefirst and second lens groups 11 and 12 to the completion of the drive ofthe final fourth lens group 14 can be reduced. Moreover, it is possibleto greaten a torque when driving and thereby to prevent the interferenceof the fourth lens group 14 with the other parts by setting a pulse rateof the fourth frame pulse motor 508 in the previous drive thereof latelythan that in the normal driving state.

Meanwhile, the driven amount of the fourth lens group 14 by the fourthframe pulse motor 508 is set so that the third and fourth lens groups 13and 14 do not interfere with each other.

When the previous drive of the fourth lens group 14 is completed, thewaiting for the reference position detection by the first and secondframes photo-reflector 510 is set. A place where the reference positionsignal (HP signal) changes from the H to the L becomes the referenceposition (HP position) of the first and second lens groups 11 and 12.When the reference position (HP position) of the first and second lensgroups 11 and 12 is detected, positional information of the first andsecond lens groups 11 and 12 is reset. In this embodiment, the HPposition of the first and second lens groups 11 and 12 is configured tobe detected by way of detecting the position of first and second frames.The movement of the first and second lens groups 11 and 12 is controlledby counting the pulse-like signal (PI signal) by the first and secondframes photo-interrupter 509 so as to acquire the movement amount of thefirst and second lens groups 11 and 12 based on the positionalinformation to the wide angle position. The wide angle position ispreviously set, but it can be changed by storing it in a nonvolatilememory such as an EEPROM (Electronically Erasable and Programmable ReadOnly Memory) or the like and rewriting it.

A specified pulse period before reaching the wide angle position is astop controlling period, in which the drive voltage is lowered inaccordance with residual pulse numbers to the wide angle position so asto reduce overrun in reaching the wide angle position. If the first andsecond lens groups 11 and 12 reach the wide angle position by countingthe PI signal by the first and second frames photo-interrupter 509, abraking control is made in order to stop the first and second lensgroups 11 and 12. An amount of overrun during the braking period is alsocounted to decide the final position of the first and second lens groups11 and 12.

Moreover, when the reference position (HP position) of the first andsecond lens groups 11 and 12 is detected, the drive of the third framepulse motor 507 in the direction of wide angle position is initiated tocontrol the third lens group 13 with the first and second lens groups 11and 12. The driving time of the third lens group 13 can be reduced bysetting the pulse rate in driving the third group pulse motor highly orrapidly than that in the normal drive.

In the third lens group 13, as described above, the retracted positionin the retracted state of the third frame 31, the optical axis entrancecompleted position of the third frame 31 at the time that the state haschanged from the retracted state to the photographable state, and thedistance from the reference position or the position of the third frame31 in the photographable state in which the focal distance during thewide-angle photographing and the telephoto photographing is changed, aredetected by the position detector structured by the T-shaped protrudedmember 350 or the L-shaped protruded member 352 and the transmissivephoto-interrupter 351. More specifically, the third lens group 13 iswaited for detecting the reference position by the third framephoto-interrupter 351. The position at which the predetermined number ofpulses from the place where the reference position signal (HP signal)detected by the third frame photo-interrupter 351 has changed from the Lto the H is detected becomes the reference position (HP position) of thethird lens group 13. When the reference position (HP position) isdetected, positional information of the third lens group 13 is reset. Inthis embodiment, the HP position of the third lens group 13 isconfigured to be detected by way of detecting the position of the thirdframe 31. The third lens group 13 is pulse-driven according to themovement amount to the wide angle position by the third frame pulsemotor 507 on the basis of the detected position (HP position). The wideangle position is previously set, but it can be changed by storing it inthe nonvolatile memory such as the EEPROM or the like and rewriting it.

Alternatively, the third frame photo-interrupter 351 may be configuredto determine the reference position (HP position) of the third lensgroup 13 by, defining that the place where the reference position signal(HP signal) detected by the third frame photo-interrupter 351 haschanged from the L to the H is the reference position (HP position) ofthe third lens group 13. As well as in this case, when the referenceposition (HP position) is detected, the positional information of thethird lens group 13 is reset, and then the third lens group 13 ispulse-driven according to the movement amount to the wide angle positionby the third frame pulse motor 507 on the basis of the detected position(HP position). The wide angle position is previously set, but it can bechanged by storing it in the nonvolatile memory such as the EEPROM orthe like and rewriting it.

In addition, the final stopping position of the third lens group 13 isthe position in which the overrun of the first and second lens groups 11and 12 is considered. That is to say, because the stopped position ofthe first and second lens groups 11 and 12 is “the wide angle positionplus the overrun amount” due to the overrun, the stopped position of thethird lens group 13 is also “the wide angle position plus “x”” inconsideration of the overrun of the first and second lens groups 11 and12. A value of the “x” is obtained by a linear calculation depending onpulse numbers between the zooming positions of the first and second lensgroups 11 and 12, the overrun amount, and a pulse number between thezooming positions of the third lens group 13. The zooming position isone of sections divided into 16 equally between the wide angle positionand the telephoto position (between W and T).

The drive of the fourth frame pulse motor 508 in the direction of a wideangle infinite position is initiated when the drive of the first andsecond lens groups 11 and 12 is completed, the reference position (HPposition) of the third lens group 13 is detected, and the third lensgroup 13 is driven more than the specified pulse number.

If the drive of the first and second lens groups 11 and 12 is notcompleted, or the third lens group 13 is not driven more than thespecified pulse from the reference position, a standby state is setuntil the drive of the first and second lens groups 11 and 12 iscompleted as well as the third lens group 13 is driven more than thespecified pulse from the reference position.

When the fourth frame pulse motor 508 is driven in the state that thedrive of the first and second lens groups 11 and 12 are not completed,the three motors are driven simultaneously and consequently, currentconsumption increases. Therefore, in such a case, only the third andfourth lens groups 13 and 14 are driven simultaneously. Moreover, whenthe fourth lens group 14 is driven before the third lens group 13reaches the position more than the specified pulse number, theinterference between the third and fourth lens groups 13 and 14 occurs.Therefore, the drive of the fourth lens group 14 is initiated after thethird lens group 13 is driven more than the specified pulse number.

The fourth lens group 14 is waited for detecting the reference positionby the fourth frame photo-interrupter 512. In addition, the drivevoltage of the fourth frame pulse motor 508 is set to be lower than thatof the normal drive so as to reduce the current consumption. A placewhere the reference position signal (HP signal) by the fourth framephoto-interrupter 512 has changed from the L to the H becomes thereference position (HP position) of the fourth lens group 14. When thereference position (HP position) of the fourth lens group 14 isdetected, positional information of the fourth lens group 14 is reset.In this embodiment, the HP position of the fourth lens group 14 isconfigured to be detected by way of detecting the position of the fourthframe 41. The fourth lens group 14 is pulse-driven according to thedetected reference position (HP position) by the fourth frame pulsemotor 508 on the basis of the movement amount to the wide angle infiniteposition. The wide angle infinite position is previously set, but it canbe changed by storing it in a nonvolatile memory such as the EEPROM orthe like and rewriting it.

FIG. 36 shows a part of a timing chart when the retractable lensretaining frame 31 moves from the retracted position to thephotographable position and when the fourth lens group 14 is moved inthe optical axis direction to perform the focusing process.

When the lens barrier 62 is opened so as to transit the state to thephotographable state, the zoom motor signal is turned from “OFF” to “ON”(time t1 in FIG. 36), and the first rotary cylinder 22 starts to movefrom the collapsed position (collapsed state) toward the subject (t1).When the first rotary cylinder 22 moves to a front position part on thesubject side and approaches the front position part (t2), the zoomposition-reference signal changes from L to H, and also the third framedrive motor 52 for driving the retractable lens retaining frame 31changes from “OFF” to “ON” to start rotating (t3). The retractable lensretaining frame 31 is driven by the movement of the third frame femalescrew member 35.

Then, the retractable lens group detector reference signal is generated,at the time that the predetermined number of pulses is counted after theoutput of the photo-interrupter 351 has fallen from “H” to “L”, when theT-shaped protruded member 350 or the L-shaped protruded member 352 goesthrough the photo-interrupter 351 from the stand by position in thecollapsed state and (t4).

In accordance with the change of the retractable lens group motor signalfrom “OFF” to “ON”, the retractable lens retaining frame 31 is made tocoincide the optical axis of own retracted lenses with the optical axisof lenses of other lens groups (i.e., the optical axis X) to place thecondition to the photographable state, and then, the retractable lensretaining frame 31 is moved toward the subject. After the zoomposition-reference signal has changed from “H” to “L” by the movement ofthe first rotary cylinder 22 (t5) and the retractable lens retainingframe 31 has moved to the subject side to change the retractable lensgroup detector reference signal from “H” to “L” (t6), the motor 53 ofthe fourth lens group 14 starts to rotate in the time (t6) to initiate afocusing process (t6).

The focusing lens detector reference signal of the fourth lens group 14changes from “L” to “H” (t7), and the motor 53 of the fourth lens group14 initiates the focusing process, and thereafter, the motor 52 formoving the retractable lens retaining frame 31 is stopped (t8). Then,the motor 53 of the fourth lens group 14 stops after the motor 52 formoving the retractable lens retaining frame 31 is stopped (t9) to endthe focusing process.

Thereafter, when the lens barrier 62 is closed for example, the statethus transits from the photographable state to the collapsed stateaccording to a collapsing process. The collapsing process follows aprocess substantially opposite of the above-described process, whichwill be described later.

In the embodiment, as described above and shown in the timing chart ofFIG. 22, the number of motors driven simultaneously is limited to two soas to reduce the current consumption as well as to shorten the timerequired for activation by the optimum drive of the motors.

Next, a case in which the barrier switch signal is changed in a closedstate during a period for monitoring the barrier switch immediatelyafter the activation of the first and second frames DC motor 503 isinitiated is described with reference to FIG. 23. If the barrier switchsignal is changed from the opened state to the closed state during theperiod, the drive of the first and second frames DC motor 503 isstopped.

Thereafter, the drive of the first and second frames DC motor 503 by amovement amount or by the specified pulse number toward the direction ofthe collapsed position is initiated. In this case, the drive voltage ismade lower so as to prevent generation of breaking and damage even ifoperating parts of the lens barrier hit against the first and secondlens groups and so on in the end of the collapsed position. By such acontrol, the first and second lens groups 11 and 12 are prevented frominterfering with the lens barrier.

[Reset Sequence]

Moreover, if the detected result of the first and second photo-reflector510 is not the collapsed position (reference position HP, signal=L), thedetected result of the third frame photo-interrupter 351 is not thecollapsed position (reference position HP, signal=H), or the detectedresult of the fourth frame photo-interrupter 512 is not the collapsedposition (reference position HP, signal=H), the reset sequence drive isexecuted.

The reset sequence is described referring to FIGS. 24A and 24B, whereinFIG. 24A is a table showing the reset sequence of the lens barrel, andFIG. 24B is a timing chart of the HP signals.

<When first and second group HP signal=H, third group HP signal=L,fourth group HP signal=L>

First, as the reset operation of the first and second lens groups 11 and12, the reference position (HP position) of the first and second lensgroups 11 and 12 is detected, and the first and second lens groups 11and 12 are moved to the wide angle position (first and second groups:Reset). Next, as the storing operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the collapsedposition (fourth group: Storage).

Subsequently, as the reset operation of the third lens group 13, thereference position (HP position) of the third lens group 13 is detected,and the third lens group 13 is moved to the wide angle position (thirdgroup: Reset).

Finally, as the reset operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the wide angleinfinite position (fourth group: Reset).

<When first and second group HP signal=H, third group HP signal=L,fourth group HP signal=H>

First, as the retiring operation of the first and second lens groups 11and 12, the first and second lens groups 11 and 12 are driven in thedirection of the telephoto and pulse-driven by the specified pulse afterthe lowering of the reference signal is detected (first and groups;Retire). Next, as the storing operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the collapsedposition (fourth group: Storage). Subsequently, as the reset operationof the first and second lens groups 11 and 12, the reference position(HP position) of the first and second lens groups 11 and 12 is detected,and the first and second lens groups 11 and 12 are moved to the wideangle position (first and second groups: Reset).

Next, as the reset operation of the third lens group 13, the referenceposition (HP position) of the third lens group 13 is detected, and thethird lens group 13 is moved to the wide angle position (third group:Reset). Finally, as the reset operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the wide angleinfinite position (fourth group: Reset).

<When first and second group HP signal=H, third group HP signal=H,fourth group HP signal=L>

<When first and second group HP signal=H, third group HP signal=H,fourth group HP signal=H>

First, as the retiring operation of the first and second lens groups 11and 12, the first and second lens groups 11 and 12 are driven in thedirection of the telephoto and pulse-driven by the specified pulse afterthe lowering of the reference signal is detected (first and groups;Retire). Next, as the storing operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the collapsedposition (fourth group: Storage). If the reference position (HPposition) of the fourth lens group 14 can be detected, the referenceposition (HP position) of the third lens group 13 is detected and thethird lens group 13 is moved to the collapsed position as the storingoperation of the third lens group 13 (third group: Storage). If thereference position (HP position) of the fourth lens group 14 cannot bedetected, because it is considered that the fourth lens group 14 isinterfered with the third lens group 13, the storing operation of thethird lens group 13 is previously carried out (third group: Storage).

If the storing operation of the third lens group 13 is completed, thestoring operation of the fourth lens group 14 is then carried out(fourth group: Storage). If the HP position is not detected at the timeof operating the storage of the third lens group 13, because it isconsidered that the third lens group 13 is interfered with the fourthlens group 14, the third lens group 13 is driven by the specified pulsecount in the direction of the telephoto as the retiring operation of thethird lens group 13 (third group: Retire). Thereafter, the storingoperation (fourth group: Storage) of the fourth lens group 14 and thestoring operation (third group: Storage) of the third lens group 13 arecarried out.

Subsequently, as the reset operation of the first and second lens groups11 and 12, the reference position (HP position) of the first and secondlens groups 11 and 12 is detected, and the first and second lens groups11 and 12 are moved to the wide angle position (first and second groups:Reset). Next, as the reset operation of the third lens group 13, thereference position (HP position) of the third lens group 13 is detected,and the third lens group 13 is moved to the wide angle position (thirdgroup: Reset). Finally, as the reset operation of the fourth lens group14, the reference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the wide angleinfinite position (fourth group: Reset).

<When first and second group HP signal=L, third group HP signal=L,fourth group HP signal=L>

<When first and second group HP signal=L, third group HP signal=L,fourth group HP signal=H>

First, as the storing operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the collapsedposition (fourth group: Storage). Next, as the storing operation of thethird lens group 13, the reference position (HP position) of the thirdlens group 13 is detected, and the third lens group 13 is moved to thecollapsed position (third group: Storage). Next, as the reset operationof the first and second lens groups 11 and 12, the reference position(HP position) of the first and second lens groups 11 and 12 is detected,and the first and second lens groups 11 and 12 are moved to the wideangle position (first and second groups: Reset). Subsequently, as thereset operation of the third lens group 13, the reference position (HPposition) of the third lens group 13 is detected, and the third lensgroup 13 is moved to the wide angle position (third group: Reset).Finally, as the reset operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the wide angleinfinite position (fourth group: Reset).

<When first and second group HP signal=L, third group HP signal=H,fourth group HP signal=L>

<When first and second group HP signal=L, third group HP signal=H,fourth group HP signal=H>

First, as the storing operation of the fourth lens group 14, thereference position (HP position) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the collapsedposition (fourth group: Storage).

If the reference position (HP position) of the fourth lens group 14 canbe detected, as the storing operation of the third lens group 13, thereference position (HP position) of the third lens group 13 is detected,and the third lens group 13 is moved to the collapsed position (thirdgroup: Storage).

If the reference position (HP position) of the fourth lens group 14cannot be detected, because it is considered that the fourth lens group14 is interfered with the third lens group 13, the storing operation ofthe third lens group 13 is previously carried out (third group:Storage). If the storing operation of the third lens group 13 iscompleted, the storing operation of the fourth lens group 14 is thencarried out (fourth group: Storage).

If the HP position is not detected at the time of operating the storageof the third lens group 13, because it is considered that the third lensgroup 13 is interfered with the fourth lens group 14, the third lensgroup 13 is driven by the specified pulse count in the direction of thetelephoto as the retiring operation of the third lens group 13 (thirdgroup: Retire).

Thereafter, the storing operation (fourth group: Storage) of the fourthlens group 14 and the storing operation (third group: Storage) of thethird lens group 13 are carried out.

Subsequently, as the reset operation of the first and second lens groups11 and 12, the reference position (HP position) of the first and secondlens groups 11 and 12 is detected, and the first and second lens groups11 and 12 are moved to the wide angle position (first and second groups:Reset). Next, as the reset operation of the third lens group 13, thereference position (HP position) of the third lens group 13 is detected,and the third lens group 13 is moved to the wide angle position (thirdgroup: Reset). Finally, as the reset operation of the fourth lens group14, the reference position (HP signal) of the fourth lens group 14 isdetected, and the fourth lens group 14 is moved to the wide angleinfinite position (fourth group: Reset).

[Storing Sequence]

The barrier switch signal changes from L to H by closing the lensbarrier 62 to initiate the storing operation. Meanwhile, the barrierswitch may be operated by mechanically closing the lens barrier 62 bymeans of an operating lever or the like, or the lens barrier 62 may beclosed by operation of the barrier switch.

The shutter of the shutter/aperture stop unit 15 is set in the fullyclosed state through the full closing control of the shutter by theshutter motor 506. Next, the aperture stop of the shutter/aperture stopunit 15 is set in the intermediately restricted state through theintermediate restricting control of the aperture stop by the first andsecond aperture stop driving motors 504 and 505. Subsequently, thestoring drive of the fourth lens group 14 is achieved through the fourthframe pulse motor 508. The standby for detecting the reference positionof the fourth frame pulse motor 508 by the fourth framephoto-interrupter 512 is set after the drive of the fourth frame pulsemotor 508 to the collapsed position is initiated.

The fourth frame pulse motor 508 is pulse-driven by the movement amountto the collapsed position from the place where the reference positionalsignal (HP signal) by the fourth frame photo-interrupter 512 changesfrom H to L. The movement amount to the collapsed position is previouslyset, but the movement amount can be changed by storing it in thenonvolatile memory such as the EEPROM or the like and rewriting it.

Next, the drive of storing the third lens group 13 is executed throughthe third frame pulse motor 507. The third lens group 13 is waited fordetecting the reference position by the third frame photo-interrupter351 by initiating the drive of the third frame pulse motor 507 in thedirection of the collapsed position.

The third lens group 13 is pulse-driven by the movement from the placewhere the reference position signal (HP signal) by the third framephoto-interrupter 351 has changed from H to L to the collapsed position.Although the movement amount to the collapsed position is setpreviously, the movement amount can be changed by storing it in thenonvolatile memory such as the EEPROM or the like and rewriting it.

The drive pulse rate of the third frame pulse motor 507 between thereference position and the collapsed position is lower than the drivepulse rate until the reference position. In this way, a smooth pulsedrive can be accomplished by changing the pulse rate in accordance withan area in which a torque is necessary.

Next, the drive of storing the first and second lens groups 11 and 12 isexecuted through the first and second frames DC motor 503. The first andsecond lens groups 11 and 12 are waited for detecting the referenceposition by the first and second frames photo-reflector 510 byinitiating the drive of the first and second frames DC motor 503 in thedirection of the collapsed position.

The control for the movement amount of the first and second lens groups11 and 12 is achieved by counting the pulse-like signal (PI signal) bythe first and second frames photo-interrupter 509 to acquire themovement amount from the place where the reference position signal (HPsignal) by the first and second frames photo-reflector 510 has changedfrom L to H to the collapsed position. Although the movement amount tothe collapsed position is set previously, the movement amount can beconfigured to be changed by storing it in the nonvolatile memory such asthe EEPROM or the like and rewriting it.

In the drive for storing the first and second lens groups 11 and 12, thePI signal is counted by the first and second frames photo-interrupter509 without dropping the voltage of the first and second frames DC motor503 before stopping it, and when the first and second lens groups 11 and12 reach the collapsed position, a breaking control is achieved in orderto stop the drive of the first and second lens groups 11 and 12. This isto prevent the first and second group DC motor from stopping at themiddle of the drive due to the dropping of voltage.

[Changing Magnification Sequence]

A sequence for operating a changing magnification is described withreference to a flow chart shown in FIG. 26.

When a changing magnification process is initiated by operating a zoomlever, zoom button or the like, whether it is necessary to retire thefourth lens group 14 is determined (step S11). It is determined in thestep S11 that the retire process for the fourth lens group 14 isrequired if the fourth lens group 14 is disposed in a nearer positionthan a predetermined position in the changing magnification process fromthe telephoto to the wide angle. Next, a direction of drive of thechanging magnification is determined (step S12). If it is the changingmagnification from the wide angle to the telephoto, the drive of thefirst and second lens groups 11 and 12 is initiated by operating thefirst and second frames DC motor 503 (step S13).

Next, whether the first and second lens groups 11 and 12 are to bestopped is determined (step S14). It is determined in the step S14 thatthe first and second lens groups 11 and 12 are stopped in a casesatisfying one of conditions in which: if a zoom driving switch operatedby changing magnification manipulation through the zoom lever or zoombutton or the like becomes off; if the first and second lens groups 11and 12 reach a position in front of a predetermined amount from thetelephoto position in the drive from the wide angle to the telephoto;and if the first and second lens groups 11 and 12 reach a position infront of a predetermined amount from the wide angle position in thedrive from the telephoto to the wide angle.

If the first and second lens groups 11 and 12 are to be stopped, whetherthe third lens group 13 is driving is judged (step S15). If the thirdlens group 13 is stopping, the stopping operation of the first andsecond lens groups 11 and 12 is executed (step S16) and the breakingoperation of the first and second lens groups 11 and 12 is executed(step S17). Subsequently, the driving direction of the changingmagnification is determined (step S18). If it is the changingmagnification from the wide angle to the telephoto, drive for correctinga position of the third lens group 13 is achieved (step S19), the driveof the aperture stop is executed (step S20), and the process iscompleted and returned from the step S20 to a process waiting state.

If it is determined that the retire process of the fourth lens group 14is determined to be required in the step S11, the retire process of thefourth lens group 14 is executed (step S21), and the process is shiftedfrom the step S21 to the step S12. In the step S12, if it is determinedthat the changing magnification driving direction is the changingmagnification from the telephoto to the wide angle, the retire processof the third lens group 13 is executed (step S22), and the process isshifted from the step S22 to the step S14.

In the step S14, if it is determined that the first and second lensgroups 11 and 12 continue to drive without stopping them, whether thethird lens group 13 is driving is judged (step S23). If the third lensgroup 13 is stopping, whether the drive of the third lens group 13 isinitiated is determined (step S24).

It is determined in the step S24 that the drive of the third lens group13 is permitted in a case satisfying one of conditions in which: if thefirst and second lens groups 11 and 12 are driven more than thespecified driven amount after the initiation of the drive of the firstand second lens groups 11 and 12; if the position of the third lensgroup 13 is away by a predetermined amount or more from the position ofthe first and second lens groups 11 and 12 when the first and secondlens groups 11 and 12 pass a predetermined zooming point in the drivingstate that the third lens group 13 is re-driven from the wide angle tothe telephoto; and if the position of the third lens group 13 isapproaching a predetermined amount or more to the position of the firstand second lens groups 11 and 12 when the first and second lens groups11 and 12 pass a predetermined zooming point in the driving state thatthe third lens group 13 is re-driven from the telephoto to the wideangle.

If the drive of the third lens group 13 is permitted in the step S24,the drive of the third lens group 13 is initiated (step S25), and theprocess is returned from the step S25 to the step S14. If the drive ofthe third lens group 13 is not permitted in the step S24, the process isreturned from the step S24 to the step S14 directly.

In the step S23, if it is judged that the third lens group 13 isdriving, whether the drive of the third lens group 13 is stopped isdetermined (step S26). It is determined in the step S26 that the thirdlens group 13 is permitted in a case satisfying one of conditions inwhich: if the position of the third lens group 13 approaches apredetermined amount or more to the position of the first and secondlens groups 11 and 12 in the drive from the wide angle to the telephoto;and if the position of the third lens group 13 is away a predeterminedor more from the position of the first and second lens groups 11 and 12in the drive from the telephoto to the wide angle.

If the stop of the third lens group 13 is permitted in the step S26, thestop of the third lens group 13 is initiated (step S27), and the processis returned from the step S27 to the step S14. In the step S26, if thestop of the third lens group 13 is not permitted, the process isreturned the step S26 to the step S14 directly.

In the step S15, if it is judged that the third lens group 13 isdriving, the stop of the third lens group 13 is initiated (step S28),and the process is shifted from the step S28 to the step S16. In thestep S18, if it is determined that the changing magnification drivingdirection is the changing magnification from the telephoto to the wideangle, a backlash operation is executed (step S29), and the process isshifted from the step S29 to the step S19.

Next, a changing magnification operation according to the flow chart isexplained in detail with reference to each of the direction of changingmagnification.

[From Wide Angle to Telephoto]

First, a changing magnification operation from the wide angle to thetelephoto is described by referring to the timing chart shown in FIG.27.

By pressing down a telephoto button of the zoom button, the telephotoswitch signal changes from H to L, and thus a variable sequence to thetelephoto direction is initiated. Initially, a retire determination ofthe fourth lens group 14 is executed (step S11).

As described above, in the retire determination of the fourth lens group14, the fourth lens group 14 is retired only if both of the followingconditions are satisfied (AND condition).

-   (1) Changing magnification drive from telephoto to the wide angle.-   (2) The fourth lens group 14 is positioned in a nearer position to    the subject (extended out position) away from a predetermined    position (retired threshold position).

However, because the above-mentioned conditions are not satisfied in thedrive from the wide angle to the telephoto, the fourth lens group 14 isnot retired.

Next, in the driving direction, whether the third lens group 13 is to beretired is determined (step S12). In the case of the changingmagnification drive from the wide angle to the telephoto, the retiringdrive of the third lens group 13 is not necessary. The drive of thefirst and second lens groups 11 and 12 is initiated through the firstand second frames DC motor 503 (step S13).

In an activating period immediately after the initiation of activationof the first and second frames DC motor 503, the drive voltage is set tobe lower than the stationary voltage in order to prevent the rushcurrent by the first and second group DC motor. After the activationperiod is lapsed, the drive voltage is increased to the stationaryvoltage.

The drive voltage between the wide angle and the telephoto is set to belower than that between the collapsed position and wide angle position.This is for the reason that a higher speed is required between thestored and wide angle positions, and hence a higher voltage is set,while a suitable voltage setting is made between the wide angle and thetelephoto so as to allow the first and second frames DC motor 503 tostop at a desired position by operation of the zoom button.

The control of the movement amount of the first and second lens groups11 and 12 is achieved by counting the pulse-like signal (PI signal) bythe first and second frames photo-interrupter 509. The zooming pointseach of which is a control reference position are set in 17 points inwhich a distance between the wide angle and the telephoto is dividedinto 16 equally.

Next, whether the first and second lens groups 11 and 12 are to bestopped is determined (step S14). In the determination for stopping thedrive of the first and second lens groups 11 and 12, if either one ofthe following conditions is satisfied (OR condition), a stopping processis executed.

-   (1) A telephoto zooming drive switch operated by the changing    magnification operation through the zoom lever or zoom button or the    like is turned off, i.e. changed from L to H.-   (2) The first and second lens groups 11 and 12 reach a position in    front of the telephoto position when driving from the wide angle to    the telephoto.

In a case that the driving of the first and second lens groups 11 and 12is continuing, the judgment of driving initiation/driving stop of thethird lens group 13 is executed in response to the status (duringdriving or stopping) of the third lens group 13 (step S23). If the thirdlens group 13 is stopping, the determination of drive initiation of thethird lens group 13 is executed (step S24), and if the initiation ispermitted, the drive of the third lens group 13 is initiated.

In the step S24, the drive of the third lens group 13 is initiated ifeither one of the following conditions is satisfied.

-   (1) The first and second lens groups 11 and 12 are driven by the    specified driven amount or more after the initiation of the drive of    the first and second lens groups 11 and 12.-   (2) During the third lens group 13 is re-driving in the drive from    the wide angle to the telephoto, the position of the third lens    group 13 is away by a predetermined amount from the position of the    first and second lens groups 11 and 12 when the first and second    lens groups 11 and 12 pass a predetermined zooming point.

Moreover, if the third lens group 13 is driving, whether the third lensgroup 13 is to be stopped is determined (step S26), and if the stop ispermitted, the drive of the third lens group 13 is stopped. In thedetermination whether the third lens group 13 is to be stopped, thethird lens group 13 is stopped if the condition that: the position ofthe third lens group 13 is positioned closer than the predetermineamount to the position of the first and second lens groups 11 and 12 inthe drive from the wide angle to the telephoto, is satisfied.

More specifically, when the first and second lens group 11 and 12 areactivated and the driven amount of the first and second lens groups 11and 12 becomes the specified pulse or more, the drive of the third lensgroup 13 is initiated. During simultaneous drive of the first, secondand third lens groups 11, 12 and 13, if the position of the third lensgroup 13 approaches by the predetermined amount to the position of thefirst and second lens groups 11 and 12, the drive of the third lensgroup 13 is stopped. Thereafter, when the first and second lens groups11 and 12 are away from the third lens group 13 and they are away fromthe third lens group 13 by a predetermined amount, the drive of thethird lens group 13 is re-started.

The drive and stop of the third lens group 13 are repeated in responseto a positional relationship among the first and second lens groups 11and 12, and the third lens group 13. Thereby, it is possible to achievethe changing magnification drive while maintaining a distance among thefirst, second, and third lens groups 11, 12 and 13.

When activating these lens groups, the influence of the rush currentcaused by the first and second frames DC motor 503 can be avoided byinitiating the drive of the third lens group 13 after the drive of thespecified amount or more of the first and second lens groups 11 and 12is carried out, and therefore the current consumption is reduced.

If the telephoto switch signal has changed from L to H before theinitiation of the initial drive of the third lens group 13, the stop ofthe first and second lens groups 11 and 12 is controlled without thesimultaneous drive of the third lens group 13 therewith. If the firstand second lens groups 11 and 12 are stopped after the stop of them isdetermined, the stop operation of the third lens group 13 is initiatedif the third lens group 13 is driving. Then, the stop of the first andsecond lens groups 11 and 12 is also initiated. A lower speed controlperiod is set during the stop operation of the first and second lensgroups 11 and 12, so that the drive voltage of the first and secondframes DC motor 503 is lowered according to the residual pulse number toa target position.

Thereby, the overrun amount of the first and second lens groups 11 and12 when reaching the target position is decreased. If the first andsecond lens groups 11 and 12 reach the target position by counting thePI signal by the first and second frames photo-interrupter 509, abreaking operation is executed in order to stop the drive of the firstand second lens groups 11 and 12. The overrun amount during the periodof breaking is also counted to decide a final position of the first andsecond lens groups 11 and 12.

After the first and second lens groups 11 and 12 are stopped, acorrection drive for the position of the third lens group 13 isexecuted. This is to compute a stopping position of the third lens group13 corresponding to the final stopping position of the first and secondlens groups 11 and 12 and drive the third lens group 13 to the stoppingposition. A target stopping position of the third lens group 13corresponding to the stopping position of the first and second lensgroups 11 and 12 is interpolatively computed from the positionalinformation of the first and second lens groups 11 and 12 every thezooming point and the positional information of the third lens group 13every the zooming point. Thereafter, the drive of the aperture stop isachieved to set a position of the aperture stop corresponding to thestopped zooming position of the third lens group 13 (step S20).

[From the Telephoto to the Wide Angle]

Next, a changing magnification operation from the telephoto to the wideangle is described with reference to the timing chart shown in FIG. 28.

By pressing down a wide angle button of the zoom button, the wide angleswitch signal changes from H to L, and a variable sequence with respectto the wide angle direction is initiated. Initially, a retiredetermination of the fourth lens group 14 is executed.

As described above, in the retire determination of the fourth lens group14, the fourth lens group is retired only if both of the followingconditions are satisfied (AND condition).

-   (1) Changing magnification drive from telephoto to the wide angle.-   (2) The fourth lens group 14 is positioned in a closer position to    the subject (extended out position) away from a predetermined    position (retired threshold position).

If the position of the fourth lens group 14 is in the nearer positionthan the predetermined position when driving from the telephoto to thewide angle, the fourth lens group 14 is retired. The retired amount isset to a range in which the third lens group 13 does not interfere withthe fourth lens group 14 in the variable operation of the third lensgroup 13.

Next, the third lens group 13 is retired. In order to prevent theinterference of the third lens group 13 with the first and second lensgroups 11 and 12 due to the initiation of the drive of the first andsecond lens groups 11 and 12, the third lens group 13 is drivenpreviously by the specified amount. The drive of the first and secondlens groups 11 and 12 is then initiated through the first and secondframes DC motor 503.

As described above, in the activation period immediately after theinitiation of activation of the first and second frames DC motor 503,the drive voltage is set to be lower than the stationary voltage inorder to prevent the rush current by the first and second frames DCmotor 503. After the activation period is lapsed, the drive voltage isincreased to the stationary voltage.

The control of the movement amount of the first and second lens groups11 and 12 is achieved by counting the pulse-like signal (PI signal) bythe first and second frames photo-interrupter 509. As described above,the zooming points each of which is a control reference position are setin 17 points in which a distance between the wide angle and thetelephoto is divided into 16 equally.

In the determination for stopping the drive of the first and second lensgroups 11 and 12, if either one of the following conditions is satisfied(OR condition), the stopping process is executed, as described above.

-   (1) A telephoto zooming drive switch operated by the changing    magnification operation through the zoom lever or zoom button or the    like is turned off, i.e., changed from L to H.-   (2) The first and second lens groups 11 and 12 reach a position in    front of the telephoto position when driving from the telephoto to    the wide angle.

In a case that the driving of the first and second lens groups 11 and 12is continuing, the determination of driving initiation/driving stop ofthe third lens group 13 is executed in response to the status (duringdriving or stopping) of the third lens group 13. If the third lens group13 is stopping, the determination for the initiation of drive of thethird lens group 13 is executed, and if the initiation is permitted, thedrive of the third lens group 13 is initiated. In the determination forinitiating the drive of the third lens group 13, the drive of the thirdlens group 13 is initiated if either one of the following conditions issatisfied (OR condition).

-   (1) The first and second lens groups 11 and 12 are driven by the    specified driven amount or more after the initiation of the drive of    the first and second lens groups 11 and 12.-   (2) During the third lens group 13 is re-driving in the drive from    the telephoto to the wide angle, and the position of the third lens    group 13 approaches by a predetermined amount to the position of the    first and second lens groups 11 and 12 when the first and second    lens groups 11 and 12 pass a predetermined zooming point.

Moreover, if the third lens group 13 is driving, the determination forstopping the drive of the third lens group 13 is executed, and if thestop is permitted, the drive of the third lens group 13 is stopped. Inthe determination whether the third lens group 13 is to be stopped, thethird lens group 13 is stopped if the condition that: the position ofthe third lens group 13 is away by the predetermine amount or more fromthe position of the first and second lens groups 11 and 12 in the drivefrom the telephoto to the wide angle, is satisfied.

More specifically, the first and second lens group 11 and 12 areactivated, and if the driven amount of the first and second lens groups11 and 12 becomes the specified amount or more, the drive of the thirdlens group 13 is initiated. During simultaneous drive of the first,second and third lens groups 11, 12 and 13, if the position of the thirdlens group 13 is away by the predetermined amount from the position ofthe first and second lens groups 11 and 12, the drive of the third lensgroup 13 is stopped. Thereafter, when the first and second lens groups11 and 12 approach to the third lens group 13 and approach to the thirdlens group 13 by the specified amount or more, the drive of the thirdlens group 13 is re-started.

The drive and stop of the third lens group 13 are repeated in responseto a positional relationship among the first and second lens groups 11and 12, and the third lens group 13. Thereby, it is possible to achievethe changing magnification drive while maintaining a distance among thefirst, second, and third lens groups 11, 12, and 13. In addition, theinfluence of the rush current of the first and second frames DC motor503 can be avoided by initiating the drive of the third lens group 13after the specified pulse or more is counted from the activation of thefirst and second lens groups 11 and 12. Thereby, it is possible toreduce the current consumption.

In the drive of the third lens group 13 to the wide angle directionduring the drive of the first and second lens groups 11 and 12,basically a control for eliminating a backlash in the movement of thethird lens group 13 is required when it is stopped. However, thebacklash eliminating control is not carried out (or prohibited) duringthe changing magnification operation so as to accomplish a smoothmovement of the third lens group 13.

If the wide angle switch signal has changed from L to H before theinitiation of the initial drive of the third lens group 13, the stop ofthe first and second lens groups 11 and 12 is controlled without thesimultaneous drive of the third lens group 13 therewith. If the firstand second lens groups 11 and 12 are stopped after the stop of them isdetermined, the stop operation of the third lens group 13 is initiatedif the third lens group 13 is driving. Then, the stop of the first andsecond lens groups 11 and 12 is also initiated.

During the stop operation of the first and second lens groups 11 and 12,a lower speed control period is set. Accordingly, the drive voltage ofthe first and second frames DC motor 503 is lowered based on theresidual pulse number to a target position. Thereby, the overrun amountof the first and second lens groups 11 and 12 when reaching the targetposition is decreased.

If the first and second lens groups 11 and 12 reach the target positionby counting the PI signal by the first and second framesphoto-interrupter 509, a breaking operation is executed in order to stopthe drive of the first and second lens groups 11 and 12. The overrunamount during the period of breaking is also counted to decide a finalposition of the first and second lens groups 11 and 12.

Furthermore, the control for eliminating the backlash of the first andsecond lens groups 11 and 12 is executed in the movement from thetelephoto to the wide angle thereof.

After the first and second lens groups 11 and 12 are stopped, acorrection drive for the position of the third lens group 13 isexecuted. This is to compute the stopping position of the third lensgroup 13 corresponding to the final stopping position of the first andsecond lens groups 11 and 12 and drive the third lens group 13 to thestopping position. A target stopping position of the third lens group 13corresponding to the stopping position of the first and second lensgroups 11 and 12 is interpolatively computed from the positionalinformation of the first and second lens groups 11 and 12 every thezooming point and the positional information of the third lens group 13every the zooming point. In the drive in the wide angle direction of thethird lens group 13, the control for eliminating the backlash of thethird lens group 13 is executed after it is stopped. Thereafter, thedrive of the aperture stop is achieved so that the aperture stop isdisposed in a position corresponding to the stopped zooming position ofthe third lens group 13.

In this example, the drive voltage of the first and second frames DCmotor 503 when it is driven in the wide angle direction is set to behigher than that in the telephoto direction in the changingmagnification operation between the wide angle and the telephoto. Thepulse rate of the third frame pulse motor 507 in the wide angledirection is set to be faster than that in the telephoto direction. Anintermittent control for the third lens group 13 is accomplished basedon the positional relationship among the first, second, and third lensgroups 11, 12, and 13 in order to maintain the distance among the first,second, and third lens groups 11, 12, and 13. Therefore, the drive speedof the third lens group 13 is set to be the same as or faster than thedrive speed of the first and second lens groups 11 and 12, in themovement in the telephoto direction.

Similarly, the drive speed of the third lens group 13 is also set to bethe same as or faster than the drive speed of the first and second lensgroups 11 and 12, in the movement in the wide angle direction. With sucha structure, the third lens group 13 is driven so that the third lensgroup 13 is not separated away from the first and second lens groups 11and 12 in the movement in the telephoto direction, and does not caughtup by the first and second lens groups 11 and 12 in the movement in thewide angle direction.

In the above-mentioned embodiments, the structure in which the thirdlens group 13 is retracted out the lens cylinder unit transverse to theoptical axis X has been described. In this structure, the retractedthird lens group 13 has the minimum outer diameter. When the third lensgroup 13 having the minimum outer diameter is retracted, a projectivesize of the lens barrel in which the third lens group 13 is retractedcan be minimized efficiently, and thus the thickness of the lens barrelcan be reduced.

Moreover, when the retracted lens is extended out of the fixed frame, asize of the device (lead screw and so on) for driving the retired lensgroup (i.e. the third lens group) is minimized by taking a structuresuch that the retracted lens is not away from the imaging planepossibly.

Furthermore, the lens retaining frame of the third lens group 13 or thethird lens group 13 itself is larger than the lens retaining frames ofthe other lens groups 11, 12, 14 or the other lens groups 11, 12, 14 inlength along the optical axis X, i.e., thickness. When the thickness ofthe third lens group 13 is larger than that of the other lens groups 11,12, and 14, consequently, the thickness of the other lens groupsdecreases. Therefore, the thickness of the lens barrel can be reducedwhen the lens barrel is in the collapsed position. As a result, thethickness of the lens barrel or a size in the direction of the opticalaxis of the lens barrel is minimized.

In addition, because the retract lens group or the third lens group 13is disposed behind and adjacent the shutter having the aperture stopfunction, the diameter of the lens barrel is less, and the retraction ofthe third lens group 13 is simplified without considering theinterference of the shutter with the lens group unit and separating theposition of the shutter from the lens cylinder unit, excessively.

Next, a structure of the plurality of lens groups is explained infurther detail. Note that the following structure or arrangement of theplurality of lens groups is exemplary, and that the structure orarrangement of the plurality of lens groups may be appropriatelymodified.

The first lens group 11 has a positive power, the second lens group 12has a negative power, the third lens group 13 has a positive power, andthe fourth lens group 14 has a positive power. A changing magnificationoperation is achieved by changing at least one of intervals between thefirst and second lens groups 11 and 12, between the second and thirdlens groups 12 and 13, and between the third and fourth lens groups 13and 14. A focusing operation is achieved by moving the fourth lens group14 along the optical axis X.

The shutter/aperture unit 15 is disposed between the second lens group12 and the third lens group 13. In other words, the shutter having thefunction of the aperture stop is positioned in front of the third lensgroup 13.

The four lens groups are provided in the lens cylinder unit. Because thethird lens group having the minimum outer diameter is retracted out ofthe lens cylinder unit without separating from the image planeexcessively, the retraction of the third lens group 13 can beaccomplished with the minimum movement and the outer diameter of thelens barrel can be minimized. In addition, the thickness of the lensbarrel is decreased by retraction of at least one lens group.

Furthermore, it is possible to provide a compact lens barrel having ahigh changing magnification ratio, 4 times or more.

Meanwhile, the lens groups may be structured from a first lens grouphaving a positive power, a second lens group having a negative power,and a third lens group having a positive power, and the third lens groupmay be retracted.

Alternatively, the lens groups may be structured by a first lens grouphaving a negative power, a second lens group having a positive power,and a third lens group having a positive power, and the second lensgroup or the third lens group may be retracted.

Each of the lens groups may be structured from one or more lenses, andthe lens groups herein indicate integral one or more lenses. Therefore,all the lens groups may be structured by one lens, respectively.

Referring now to FIG. 17A to FIG. 19, a camera including an opticalsystem device having the lens barrel according to the present inventionas shown in the first embodiment will be described as a secondembodiment.

Although the lens barrel is applied to the camera here, the lens barrelis also applicable to a lens driving apparatus, an optical device, etc.In addition, the lens barrel according to the present invention as shownin the first embodiment is also applicable to a mobile informationterminal such as so-called PDA (Personal Data Assistant), a mobile phoneand so on, having a camera function or functional part installedtherein.

Many of such mobile information terminals have the function and thestructure substantially identical to the function and the structure ofthe camera, although the appearance is slightly different. Therefore,the optical system device including the lens barrel according to thepresent invention may be employed in such mobile information terminals.Further, the lens barrel according to the present invention may beapplied to an image forming device such as a copying machine, a scanneror the like.

As shown in FIG. 17A, FIG. 17B and FIG. 18, the camera includes an imagepickup lens 101, a shutter release button 102, a zoom lever 103, aviewfinder 104, a strobe light 105, a liquid crystal display (LCD) 106,an operating button 107, a power switch 108, a memory card slot 109, anexpansion card slot 110, the barrier-operating element 301 and so on.

Furthermore, as shown in FIG. 19, the camera also includes aphotodetector 201, a signal-processing unit 202, an image-processingunit 203, a central processing unit (CPU) 204, a semiconductor memory205, and an expansion card 206. Although it is not shown specifically,electric power is supplied from a battery as an electric source to theabove-mentioned parts to operate the parts.

The photodetector 201 serves as an area sensor such as a CCD (ChargeCoupled Device) image pickup element or the like to read an image of asubject to be photographed, that is, of an photographing subject, formedby the image pickup lens 101, which is a photographing optical system.As the image pickup lens 101, the optical system device including thelens barrel according to the present invention as described in the firstembodiment is employed.

More specifically, the optical system device includes a plurality lensgroups as optical elements and a telescopic cylinder unit retaining thelens groups, which structure the lens barrel.

The lens barrel has a mechanism of retaining the respective lens groupsin the lens cylinder such that the lens groups can be moved in responseto the movement of the lens cylinder along the optical axis of the lensgroups, similarly to the above-mentioned embodiment. The image pickuplens 101 to be integrated in the camera is generally integrated in theform of this optical system device.

An output from the photodetector 201 is processed by thesignal-processing unit 202, which is controlled by the centralprocessing unit 204, and is converted into digital image information.The image information digitized by the signal-processing unit 202 issubjected to a predetermined image processing in the image-processingunit 203 which is also controlled by the central processing unit 204,and then stored in the semiconductor memory 205 such as a non-volatilememory.

In this case, the semiconductor memory 205 may be a memory card insertedin the memory card slot 109, or may be a semiconductor memory integratedin a body of the camera. The liquid crystal display 106 may display thephotographing image or may display the image stored in the semiconductormemory 205. An image stored in the semiconductor memory 205 can betransmitted to the outside of the camera via the expansion card 206inserted in the expansion card slot 110. Meanwhile, the above-mentionedcentral calculation processing device 501 shown in FIG. 21 to controlthe drive of the lens groups may be included in the central processingunit 204, otherwise structured by use of other micro-processorconnecting with the central calculation processing device 501.

The image pickup lens 101 is embedded within the camera body into acollapsed or stored state as shown in FIG. 17A when being transported orcarried by a user, and the lens barrier 62 is closed. When the useroperates the barrier-operating element 301 to open the lens barrier 62,the power is turned on and the lens barrel is moved from the closedposition to an opened position and projected from the camera body asshown in FIG. 17B, so that the photographing state is established. Atthis time, the image pickup lens 101 within the lens barrel is set sothat the respective lens groups of the optical systems structuring azoom lens are arranged, for example, at a short focal length wide angleposition.

When the zoom lever 103 is operated, the arrangement of the respectivelens groups in the optical system is changed through the movement of thelens groups along the optical axis, and therefore, the zoom can bevaried to the telephoto position.

Preferably, an optical system of the viewfinder 104 is configured suchthat the zooming is varied in association with the change of the angleof field of the image pickup lens 101.

In many cases, focusing is achieved by half-pressing operation of theshutter release button 102. The focusing with the zoom lens in the lensbarrel according to the present invention is achieved mainly by movingthe fourth lens group 14, although it is not limited thereto. When theshutter release button 102 is further pressed to a completely pressedstate, the photographing is achieved, and subsequently the processing asdescribed above is performed.

In order to display the image stored in the semiconductor memory 205 onthe liquid crystal display 106 or transmit the same to the outside ofthe camera via the expansion card 206, the operating button 107 isoperated in a predetermined manner. The semiconductor memory 205 and thecommunication card 206 or the like are used by being inserted in aspecific or multi-purpose slot such as the memory card slot 109 and thecommunication car slot 110.

When the image pickup lens 101 is in the stored state, the third lensgroup 13 is retracted from the optical axis to the retracted positionoutside of the telescopic cylinder unit, and hence is stored in a linewith the first lens group 11 and the second lens group 12 in ajuxtaposed manner. Therefore, further reduction in thickness of thecamera is achieved.

Generally, because a viewfinder mechanism is disposed above of the lensbarrel, therefore, certain camera operation is easy. Moreover, if thelens barrel includes a zoom changing magnification mechanism, becausethe viewfinder mechanism also needs the zoom changing magnificationmechanism, it is preferable that a drive source (DC motor, pulse motoror the like) for conducting the zoom changing magnification operationand a transmission mechanism (gear connecting mechanism or the like) fortransferring a driving force of the drive source to the lens groups aredisposed adjacent the viewfinder mechanism. For example, if theviewfinder mechanism is disposed on upper and left position of the lensbarrel, the drive source and the transmission mechanism are disposedadjacent the upper and left position of the lens barrel to use a limitedspace effectively.

When the frame for the retractable lens group (third lens group 13according to the embodiment) is retracted, the retaining frame is storedbelow the lens barrel in consideration of the left space. The space islower and right position or lower and left position of the lens barrel.In the embodiment, the space is disposed on the lower and right positionof the lens barrel to store the retaining frame of the retracted thirdlens group. The above-mentioned storage part of the fixed lens cylinderis disposed at the position.

The drive source and the transmission mechanism for driving the lensgroups are disposed at the lower and left position. As a result, aminiaturized lens barrel can be accomplished with effective use offourth corners, the upper and left position, the upper and rightposition, the lower and right position, and the lower and left positionof a lens barrel.

Although the present invention has been described in terms of exemplaryembodiments, it is not limited thereto. It should be appreciated thatvariations may be made in the embodiments described by persons skilledin the art without departing from the scope of the present invention asdefined by the following claims. Moreover, no element and component inthe present disclosure is intended to be dedicated to the publicregardless of whether the element or component is explicitly recited inthe following claims.

INDUSTRIAL APPLICABILITY

The lens barrel according to the present invention is applicable to anyportable device having a camera function or functional part installedtherein. The example of which is a mobile information terminal such asso-called PDA (Personal Data Assistant), a mobile phone, and so onalthough it is not limited thereto. The lens barrel according to thepresent invention may also be applied to an image forming device such asa copying machine, a scanner and so on, and to a lens driving apparatusand an optical device as well.

1. A lens mechanism, comprising: a) a plurality of lens groups eachhaving at least one lens; b) a plurality of lens retaining frames whichretain a corresponding one of the plurality of lens groups, theplurality of lens groups being located on a photographing optical axisin a photographable state; c) a telescopic cylinder containing thereinthe plurality of lens groups and the plurality of lens retaining framesin the photographable state; d) a lens retaining frame driving deviceconfigured to drive at least one of the lens retaining frames; at leastone of the plurality of lens groups being collapsed to store theplurality of lens groups in a collapsed state and the at least one ofthe plurality of lens groups being expanded in the photographable state,the plurality of lens retaining frames including a retractable lensretaining frame configured to retain at least another one of theplurality of lens groups, configured to retract the at least another oneof the plurality of lens groups from the photographing optical axis to aretracted position out of the telescopic cylinder in the collapsed stateand configured to move the at least another one of the plurality of lensgroups from the retracted position to a position on the photographingoptical axis in the photographable state; e) a moving member which movesin a direction along the photographing optical axis; the at leastanother one of the plurality of lens groups being moved between theretracted position and a position on the photographing optical axis inaccordance with the movement of the moving member in the direction alongthe photographing optical axis; and f) a position detector configured todetect a change in a position of the moving member.
 2. The lensmechanism according to claim 1, wherein the retractable lens retainingframe is moved in the direction along the photographing optical axis andthe at least another one of the plurality of lens groups is moved on thephotographing optical axis in accordance with the movement of the movingmember in the direction along the photographing optical axis.
 3. Thelens mechanism according to claim 1, wherein the retracted position issubstantially out of the telescopic cylinder and is distant from thephotographing optical axis.
 4. The lens mechanism according to claim 1,wherein the at least another one of the plurality of lens groups isconfigured to be retracted within a thickness range of the telescopiccylinder in the collapsed state in the direction of the photographingoptical axis.
 5. The lens mechanism according to claim 1, wherein theretractable lens retaining frame includes a cam portion, the movingmember includes a contact portion configured to have contact with thecam portion, and the cam portion is configured to change a position ofthe at least another one of the plurality of lens groups between theretracted position and a position on the photographing optical axis. 6.The lens mechanism according to claim 5, wherein the cam portion isconfigured to change a position of the at least another one of theplurality of lens groups on the photographing optical axis.
 7. The lensmechanism according to claim 5, further comprising a biasing memberconfigured to bias the contact portion to always have contact with thecam portion.
 8. The lens mechanism according to claim 5, furthercomprising a biasing member configured to bias the retractable lensretaining frame in the direction along the photographing optical axis.9. The lens mechanism according to claim 1, further comprising a biasingmember which biases the retractable lens retaining frame in thedirection in which the at least another one of the plurality of lensgroups travels to a position on the photographing optical axis from theretracted position.
 10. The lens mechanism according to claim 1, whereinthe position detector includes a detected portion provided on the movingmember and a detecting portion detecting that the detected position haspassed a predetermined position.
 11. The lens mechanism according toclaim 1, further comprising a fixed frame holding the telescopiccylinder, wherein the fixed frame includes a guide groove which isparallel to the photographing optical axis, and the moving memberincludes a rotation-preventing projection fitting to the guide grooveand is driven in the direction along the photographing optical axis by alead screw.
 12. The lens mechanism according to claim 1, wherein the atleast another one of the plurality of lens groups in the retractedposition is detected according to the output of the position detector.13. The lens mechanism according to claim 1, wherein the telescopiccylinder is housed and driven according to the output of the positiondetector.
 14. The lens mechanism according to claim 1, wherein the atleast another one of the plurality of lens groups in the retractedposition is detected according to the output of the position detector,and the telescopic cylinder is housed and driven after the at leastanother one of the plurality of lens groups in the retracted position isdetected.
 15. The lens mechanism according to claim 1, furthercomprising at least one optical lens element located nearer to an imageplane in the lens mechanism than the retractable lens retaining frame,wherein the position detector permits movement of the optical lenselement according to the detected result of the position detector.
 16. Amethod of controlling a lens mechanism including a) a plurality of lensgroups each having at least one lens; b) a plurality of lens retainingframes which retain a corresponding one of the plurality of lens groups,the plurality of lens groups being located on a photographing opticalaxis in a photographable state; c) a telescopic cylinder containingtherein the plurality of lens groups and the plurality of lens retainingframes in the photographable state; d) a lens retaining frame drivingdevice configured to drive at least one of the lens retaining frames, atleast one of the plurality of lens groups being collapsed to store theplurality of lens groups in a collapsed state and the at least one ofthe plurality of lens groups being expanded in the photographable state,the plurality of lens retaining frames including a retractable lensretaining frame configured to retain at least another one of theplurality of lens groups, configured to retract the at least another oneof the plurality of lens groups from the photographing optical axis to aretracted position out of the telescopic cylinder in the collapsed stateand configured to move the at least another one of the plurality of lensgroups from the retracted position to a position on the photographingoptical axis in the photographable state; e) a moving member which movesin a direction along the photographing optical axis, the at leastanother one of the plurality of lens groups being moved between theretracted position and a position on the photographing optical axisaccording to the movement of the moving member in the direction alongthe photographing optical axis; and f) a position detector configured todetect a change in a position of the moving member, the methodcomprising: driving the moving member in the direction along thephotographing optical axis; and housing the at least another one of theplurality of lens groups by retracting the at least another one of theplurality of lens groups out of the telescopic cylinder according to theoutput of the position detector.
 17. The method according to claim 16,further comprising the steps of: detecting that the at least another oneof the plurality of lens groups is located in the retracted positionaccording to the output of the position detector; and housing anddriving the telescopic cylinder after the at least another one of theplurality of lens groups in the retracted position is detected.